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THE  following  pages  are  presented  with  the  purpose  of  affording 
students  a  comprehensive  view  of  modern  mineralogy  rather  than  a 
detailed  knowledge  of  many  minerals  The  -minerals  selected  for 
description  are  not  necessarily  those  that  are  most  common  nor  those 
that  occur  in  greatest  quantity  The  list  includes  those  that  are  of 
scientific  interest  or  of  economic  importance,  and,  in  addition,  those 
that  illustrate  some  principle  employed  in  the  classification  of  minerals. 
The  volume  is  not  a  reference  book.  It  is  offered  solely  as  a  textbook 
It  does  not  pretend  to  furnish  a  complete  discussion  of  the  mineral 
kingdom,  nor  a  means  of  determining  the  nature  of  any  mineral  that 
may  be  met  with  The  chapters  devoted  to  the  processes  of  deter- 
minative mineralogy  are  brief ,  and  the  familiar  "  key  to  the  determina- 
tion of  species  "  is  omitted  In  place  of  the  latter  is  a  simple  guide 
to  the  descriptions  of  minerals  to  be  found  in  the  body  of  the  text. 
For  more  complete  determinative  tables  the  reader  is  referred  to  one 
of  the  many  good  books  that  are  devoted  entirely  to  this  phase  of  the 
subject.  In  the  descriptions  of  the  characteristic  crystals  of  minerals 
both  the  Naumann  and  the  Miller  systems  of  notation  are  employed, 
the  former  because  of  its  almost  general  use  in  the  more  important  refer- 
ence books  and  the  latter  because  of  its  almost  universal  use  in  modern 
crystallography  investigations  The  student  must  be  familiar  with 
both  notations  It  is  thought  that  this  familiarity  can  be  best  acquired 
by  employing  the  two  notations  side  by  side 

In  preparing  the  descriptive  matter  the  author  has  made  extensive 
use  of  Hintze's  Handbuch  der  Mvrwralogie.  The  figures  illustrating 
crystal  forms  are  taken  from  many  sources.  A  few  illustrations  have 


viii  PREFACE 

been  made  especially  for  this  volume.  Figures  copied  to  illustrate 
special  features  are  accredited  to  their  authors.  The  statistics  are 
mainly  from  the  Mineral  Resources  of  the  Umted  States  They  are 
given  for  the  year  1912  because  this  was  a  more  nearly  normal  year  in 
trade  than  any  that  has  followed 

The  author  is  under  obligation  to  the  McGraw-Hill  Book  Company 
for  permission  to  reproduce  a  number  of  illustrations  originally  published 
in  his  Elements  of  Crystallography,  and  also  for  the  use  of  the  original 
engravings  m  making  the  plates  for  Figures  n,  33, 71, 90,  no,  114, 115, 
118, 160, 191, 194,  224,  240,  and  248. 

W.  S.  BAYLEY. 






























AND  Aero  RADICALS,        ,                  .  483 







INDEX  529 



1  Sodium  fluosihcate  crystals                       ...  14 

2  Potassium  fluosihcate  crystals  14 

3  Cross-section  of  symmetrical  vein  21 

4  Cross-section  of  vein  in  green  porphyry  24 

5  Dionte  dike  cutting  granite  gneiss  26 

6  Vein  in  Griffith  mine  27 

7  Vein  forming  original  ore-body,  Butte,  Mont  27 

8  Druse  of  Smithsonite  28 

9  Geodes  containing  calcite  29 

10  Alteration  of  ohvine  into  serpentine  31 

11  Etch  figures  in  cubic  face  of  diamond  38 

12  Crystal  of  diamond  with  rounded  edges  and  faces  38 

13  Octahedron  of  diamond  38 

14  Principal  "cuts"  of  diamonds  42 

15  Premier  diamond  mines  m  South  Africa  43 

1 6  The  Cullman  diamond  43 

17  Gems  cut  from  Culhnan  diamond    .  44 

1 8  The  Tiffany  diamond  44 

19  Sulphur  crystals  47 

20  Distorted  crystal  of  sulphur.                                       ...  47 

21  Copper  crystal  53 

22  Crystal  of  copper  from  ELeweenaw  Point  53 

23  Plate  of  silver  from  Comagas  Mine,  Cobalt  57 
24.  Octahedral  skeleton  crystal  of  gold  with  etched  faces  58 

25  Iron  meteonte  65 

26  Widmanstatten  figures  on  etched  surface  of  meteonte  66 

27  Realgar  crystal                        . .  70 

28  Stibrute  crystal  72 

29  Galena  crystal  81 

30  Galena  crystals                                                                     .  82 

31  Chalcocite  crystal  85 

32  Complex  chalcocite  twin  85 

33  Tetrahedral  crystal  of  sphalerite  88 
34.  Sphalerite  crystal                                ,  88 

35  Sphalerite  octahedron                    .  88 

36  Greenockite  crystal                        .      .  91 

37  Pyrrhotite  crystal. 92 



38  Cinnabar  crystals  98 

39  Group  of  pyrite  crystals  in  which  the  cube  predominates  102 

40  Pyrite  crystals  on  which  0(111)  predominates  102 

41  Pyrite  crystal  102 

42  Group  of  pyrite  crystals  103 

43  Pyrite  mterpenetration  twin  103 

44  Marcasite  crystal  no 

45  Marcasite  crystal  with  forms  as  indicated  m  Fig  44  no 

46  Twin  of  marcasite  no 

47  Spearhead  group  of  marcasite  no 

48  Arsenopynte  crystals  112 

49  Crystal  of  pyrargyrite  ng 

50  Crystal  of  proustite  119 

51  Bournonite  crystal  121 

52  Bournonite  fourlmg  twinned  121 

53  Enargite  crystal  123 

54  Stephanite  crystal  125 

55  Tetrahednte  crystal  I28 

56  Chalcopynte  crystal  I3I 

57  Chalcopynte  131 

58  Chalcopynte  twin  13! 

59  Hopper-shaped  cube  of  halite  ,     135 

60  Group  of  fluonte  crystals  from  Weardale  Co  139 

6 1  Crystal  of  fluonte  !4O 

62  Interpenetration  cubes  of  fluonte,  twin-  140 

63  Photographs  of  snow  crystals  147 

64  Zmcite  crystal  !^0 

65  Hematite  crystals  j^ 

66  Corundum  crystal  j^ 

67  Corundum  crystal  ^5 

68  Corundum  crystal  I^ 

69  Quartz  crystal  exhibiting  rhombohedral  symmetry  159 

70  Ideal  (A)  and  distorted  (B)  quartz  crystals       .  159 

71  Etch  figures  on  two  quartz  crystals  of  the  same  form  ,     160 

72  Group  of  quartz  crystals  ,  jgo 

73  Tapenng  quartz  crystal  X5X 

74  Quartz  crystal  ,     ufa 

75  Supplementary  twins  of  quartz.          ,  ,162 

76  Quartz  twinned  I0*3 

77  Cassitente  crystal  ,  .  .  169 

78  Cassitente  crystal                                                          ,  ^ 

79  Cassitente  twinned  j$g 

80  Rutile  crystals  172 
81.  Rutile  eightluig  twinned                                        ,     .              ,  2 



82  Rutile  twinned    .  .    172 

83  Rutile  cycbc  sixling  twinned  j^ 

84  Rutile  twinned                                          ^. 

85  Anatase  crystal                                    I77 

86  Anatase  crystal                                     I77 

87  Brookite  crystals                                   I73 

88  Brucite  crystal  f        !32 

89  Limonite  stalactites  in  Silverbow  mine.    .  ,  184 

90  Botryoidal  hmorute                                                . .  jg^ 

91  Pisohtic  bauxite  from  near  Rock  Run                    .  187 

92  Diaspore  crystals                                                ,  I9O 

93  Mangamte  crystal                                                  . .  I92 

94  Group  of  prismatic  mangamte  crystals  192 

95  Mangamte  crystal  twinned                          .                      .  193 

96  Spinel  twin                                                  .  .  ig5 

97  Spinel  crystal                                             .  196 

98  Magnetite  crystal                                       .  198 

99  Chrysoberyl  crystal  203 

100  Chrysoberyl  twinned                .                     .  203 

101  Chrysoberyl  pseudohexagonal  sixling  .  203 

102  Hausmanmte                                      .        .  204 
103.  Borax  crystal          .                                  .  207 

104  Colemamte  crystals                          ....  209 

105  Boracite  crystal                        211 

106  Calcite  crystal            .                       214 

107  Calcite  crystals                                 214 

108  Calcite  crystals                                      214 

109  Calcite                                     .           .......  214 

no  Prismatic  crystals  of  calcite        215 

in    Calcite              .                   215 

112  Calcite   twin  and  polysynthetic  trilling.  215 

113  Calcite                                                 216 

114  Artificial  twin  of  calcite  ,      216 

115  Thin  section  of  marble  viewed  by  polarized  fight.  .    216 

1 16.  Aragonite  crystal                   224 

117.  Aragonite  twin                               224 

118  Tnlhng  of  aragomte                        224 

119  Withente  twinned  .        226 

120.  Cerussite  crystal  .  .        227 

121.  Cerussite  tnllmg  twinned                 .     ,  227 

122.  Cerussite  trilling  twinned  227 

123.  Radiate  groups  of  cerussite  on  galena  . .  -228 

124.  Dolomite  crystal.  .      -        229 

125.  Group  of  dolomite  crystals.       .  230 



126  Malachite  crystal  .232 

127  Azurite  crystals  233 

128  Trona  crystal  235 

129  Gayhissite  crystal  235 

130  Glauberite  crystal  237 

131  Thenardite  crystal  237 

132  Thenardite  twinned  237 

133.  Bante  crystals  239 

134.  Bante  crystals  240 

135.  Celestite  crystals  241 
136   Anglesite  crystal  243 
137.  Anglesite  crystal  243 
138   Anglesite  crystal  243 

139.  Gypsum  crystals  247 

140.  Gypsum  twinned  247 

141.  Gypsum  twinned  248 

142.  Epsomite  crystal  250 

143.  Hanksite  crystal  252 

144.  Crocoite  crystals  253 

145.  Scheelite  crystal  .  255 

146.  Scheelite  crystal  255 

147  Wulfemte  crystal  257 

148  Wulfemte  crystal  ,  .  257 

149  Wolframite  crystal  250 
150.  Monazite  crystal                                                                               ,  264 

151  Xenotime -crystals  265 

152  Apatite  crystal  ,  267 

153  Apatite  crystal                                                .   .  267 
154-  Vanadimte  crystal                               .  262 
155.  Skeleton  crystal  of  vanadmite                                .                         .272 

156  Amblygomte  crystal  ,  2^ 

157.  Lazulite  crystals      ,  .     ,  .  2^6 

158  Olivemte  crystal.          ,  27^ 

159  Skorodite  crystal  286 

160  Radiate  wavelhte  on  a  rock  surface  .  ,   ,     287 
161.  Columbite  crystals      .  ,     ^ 

162  Samarskite  crystals       « .  .          .  ,  >       .        297 

163  Olivme  crystals  ,  ,  3P3 

164  Willemite  crystal  ,        ,  3O7 

165  Phenacite  crystal                                                                      ,        3Og 
166.  Garnet  crystal  (natural  size)  .  3IO 

167  Garnet  crystals  ,,  ,  ,          .310 

168  Garnet  crystal  ,  31O 

16^)  Nephehue  crystal,  ,  I 




.    , 

170  Zircon  crystals  .......  .317 

171  Zircon  twinned  „. 

172  Thorite  crystal  3Ip 

173  Andalusite  crystals  ,2O 

174  Topaz  crystals  32- 

175  Topaz  crystal  323 

176  Topaz  crystal  ,24 

177  Danbunte  crystal  325 

178  Zoisite  crystal  ^ 

179  Epidote  crystal  ^2g 
1  80   Epidote  crystals  328 

181  Chondrodite  crystal  333 

182  Datolite  crystal  334 

183  Staurolite  crystal  337 

184  Staurolite  crystal  twinned  337 

185  Staurolite  crystal  twinned  33-7 
1  86    Sodalite  mterpenetration  twin  of  t\vo  dodecahedrons  340 
187    Prehmte  crystal            -  344 
1  88.  Axinite  crystal  346 

189  Axmite  crystal  .    346 

190  Dioptase  crystal  347 

191  Percussion  figure  348 

192.  Biotite  crystal  349 

193.  Biotite  twinned  about  a  plane  .    349 

194  Etch  figures  356 

195  Muscovite  crystal  356 

196  Beryl  crystals  ..                                                           360 

197  Beryl  crystals  .                                                          .    360 
198.  Cross-section  of  pyroxene  *  ,                                     363 

199  Enstatite  crystal.  .                                                             366 

200  Wollastomte  crystal  *                           .    368 

201.  Augite  crystal    .  .                                                           37* 

202.  Augite  twinned  .                                                   371 

203  Interpenetration  twin  of  augite  .    371 

204  Diopside  crystals       ,  .                                                            372 
205,  Hedenbergite  crystal  373 
206*  Acnute  crystal     ,  3  76 
207.  Spodumene  crystal.     .  .                                                            379 
208  Rhodonite  crystals  3&> 
209;.  Ampibole  crystals  *      3^4 
210.  Kyanite  crystals  394 
211   Bladed  kyanite  crystals  in  a  micaceous  quartz  schist  395 

212.  Calarmne  crystals           ,  30 

213.  Orthoclase  crystals  .     .              .  »  ,  ,     ......    410 



214  Orthoclase  crystals  •   •  •  • » 410 

215  Carlsbad  mterpenetration  twins  of  orthoclasc  410 

216  Contact  twin  of  orthoclase  according  to  the  Carlsbad  law  4IO 

217  Baveno  twins  of  orthoclase  411 

218  Manebach  twin  of  orthoclase  411 

219  Section  of  mirocline  viewed  between  crossed  nicols  4x4 

220  Adulana  crystal  414 

221  Albite  crystals  419 

222  Albite  twinned  419 

223  Albite  twinned  419 

224  Twinning  stnations  on  cleavage  piece  of  ohgoclasc  420 

225  Albite  twins  with  the  crystal  axis  420 

226  Position  of  "rhombic  sections"  in  albite  .    420 

227  Diagram  of  crystal  of  tnclimc  feldspar                                f  420 

228  Potash-oligoclase  crystal  422 

229  Scapohte  crystals  424 

230  Chntonite  twinned  according;  to  the  mica  law  427 

231  Cknochlore  crystal  430 

232  Clmochlore  twinned  according  to  mica  law  430 

233  Chnochlore  with  same  forms  as  m  Fig  232  430 

234  Clmochlore  tnllmg  twinned  according  to  mica  law  430 

235  Pennimte  crystal  430 

236  Pennimte  crystal  twinned  430 

237  Vesuviamte  crystals  .  433 
238.  Tourmaline  crystals  436 

239  Tourmaline  crystals  436 

240  Cooling  crystal  of  tourmaline  436 

241  Cordiente  crystal  .         . ,  439 

242  Apophylhte  crystals  444 

243  Heulandite  crystal         ,  ,  447 

244  Heulandite,  var  beaumontJte  .       .  447 

245  Philhpsite  mterpenetration  twin  ,       ,        448 

246  Phillipsite  ,  448 

247  Harmotome  fourling  twinned  like  pmllipsite                              .  449 

248  Sheaf-like  aggregates  of  stilbite  ,   .  450 

249  Laumontite  crystal  452 

250  Divergent  groups  of  scolecite  crystals  453 

251  Scoleate  crystal  ,  453 

252  Natrohte  crystals                                                               ,   ,    .  434 
253.  Thomsomte  crystal                                      .        ,            ...  456 

254  Chabazite  crystal  t  4^7 

255  Chabazite  mterpenetration  twin                           .  .    457 
256.  Phacohte  with  same  form  as  in  Fig  254                    .  457 
257   Analate  crystal                                                                     ,       t      4 




258  Analcite  crystal     .   ,   ,  .  ,  4-9 

259  Ilmemte  crystal  463 

260  Titanite  crystal  4g4 

261  Titanite  crystal  4^4 

262  Titanite  crystal  454 

263  Simple  blowpipes  4gg 

264  Bellows  for  use  with  blowpipe  468 

265  Candle  flame  showing  three  mantles  47o 

266  Reducing  flame  4yZ 

267  Oxidizing  flame  4^r 
268.  Props  and  position  of  charcoal  4^5 





Definition  of  Mineral. — A  mineral  is  a  definite  inorganic,  chem- 
ical compound  that  occurs  as  a  part  of  the  earth's  crust.  It  possesses 
characters  which  are  functions  of  its  composition  and  its  structure. 
Most  minerals  are  crystallized,  but  a  few  have  been  found  only  in  an 
amorphous,  colloidal  condition.  These  are  regarded  as  gels,  or  solid 

The  most  essential  feature  of  a  mineral  is  its  chemical  composition, 
since  upon  this  are  believed  to  be  dependent  all  its  other  properties. 

Chemical  Substances  Occurring  as  Minerals.— The  chemical 
substances  found  native  as  minerals  may  be  classed  as  elements  and 
compounds  The  latter  comprise  chlorides,  fluorides,  sulphides,  oxides, 
hydroxides,  the  salts  of  carbonic,  sulphuric,  phosphorus,  arsenic,  anti- 
mony and  silicic  acids,  a  large  series  of  complicated  compounds  known 
as  the  sulpho-salts,  a  few  derivatives  of  certain  metallic  acids— the 
aluminates  and  the  ferrites— besides  other  salts  of  rarer  occurrence, 
some  simple  and  others  exceedingly  complicated,  and  possibly  many 
solid  solutions  of  gels  or  of  a  gel  and  a  crystalloid.  In  some  of  these 
classes  all  the  compounds  are  anhydrous.  In  others,  some  groups  are 
anhydrous  while  the  members  of  other  groups  contain  one  or  more 
molecules  of  water  of  crystallization. 

The  sulphides,  chlorides  and  fluorides  are  derivatives  of  EfeS,  HC1, 
and  ifeFs,  respectively.  They  may  be  regarded  as  having  been  pro- 
duced from  these  compounds  by  the  replacement  of  the  hydrogen  by 
metals.  Illustrations:  CuaS,  CuS,  NaCl,  CaF2. 


The  hydroxides  and  the  oxides  may  be  looked  upon  as  derivatives  of 
water,  the  hydroxides  through  the  replacement  of  one  atom  of  hydrogen 
by  a  metal,  and  the  oxides  through  the  replacement  of  both  hydrogen 


atoms     The  mineral,  bructte,  according  to  this  view  is  Mg/       , 

H(OH)  X)H 

derived  from  rr^rr\  by  replacement  of  two  hydrogen  atoms  in  two 

molecules  of  water  by  one  atom  of  Mg     Cuprite  is        >0,  and  tenonte 


CuO,  the  former  derived  by  replacement  of  each  atom  of  hydrogen  m 
one  molecule  of  water  by  an  atom  of  Cu,  and  the  latter  by  replacement 
of  the  two  hydrogens  by  a  single  Cu 

The  salts  of  carbonic  acid  (H2COs)  are  the  carbonates,  those  of  sul- 
phuric acid  (HaSO*)  the  sulphates,  those  of  orthophosphoric  acid 
(HsP04)  the  phosphates,  those  of  orthoarsemc  acid  (HsAsO^  the  arsen- 
ates,  those  of  orthoantimomc  acid  (HaSbO-i)  the  antimonates  and  those 
of  the  silicic  acids,  the  silicates  There  are,  in  addition,  a  few  arsenites 
and  antimonites  that  are  salts  of  arsemous  (HsAsOa)  and  antimonous 
(H3Sb03)  acids 

The  principal  silicic  acids  whose  salts  occur  as  minerals  are  normal 
silicic  acid  (H4Si04),  metasihcic  acid  (HaSiOj),  and  tribilicic  acid 
(HiSiaOs)  The  metasihcic  and  the  tribihcic  acids  may  be  regarded 
as  normal  silicic  acid  from  which  water  has  been  abstracted,  m  the  same 
way  that  pyrosulphuric  acid  is  ordinary  sulphuric  acid  less  H20,  thus: 
2H2SO*-  H20  »  H2S207 

(HO)4Si-H20=H2Si03,  metasihcic  acid 
3(HO)4Si-4H20=H4Si30«,  tnsihcic  acid. 

Faydite  is  Fe2Si04,  wollastonite,  CaSiOs,  and  ortkoctase,  KAlSisOs- 
The  alummates  and  ferntes  may  be  regarded  as  salts  of  the  hypothet- 
ical acids  AIO(OH)  and  FeO(OH),  both  of  which  exist  as  minerals, 
the  first  under  the  name  dtaspore  and  the  second  under  the  name 

yO— A10 

goethite.    Spinel  is  the  magnesium  aluminate,  Mg<f  .(MgAfeO*), 

and  magnofernte  the  corresponding  ferrate  MgFe204.    The  very  com- 

X)— FeO 
mon  mineral  magnetite  is  the  iron  ferrate  Fe<;  ,  or  FesO*,    In 


this  compound  the  iron  is  partly  in  the  ferrous  and  partly  in  the  ferric 


There  are  other  minerals  that  differ  from  those  of  the  classes  above 
mentioned  in  containing  more  or  less  water  of  crystallization  These 
are  usually  separated  from  those  m  which  there  is  no  water  of  crystal- 
lization under  the  name  of  hydrous  salts 

Besides  the  classes  of  minerals  considered  there  are  others  which 
appear  to  be  double  salts,  m  which  two  substances  that  may  exist 
independently  occur  combined  to  form  a  third  substance  with  prop- 
erties different  from  those  of  its  components  Cryolite,  sNaF-AlFa 
or  NasAlFe,  is  an  example  The  sulpho-salts  furnish  many  other 

Further,  a  large  number  of  minerals  are  apparently  isomorphous 
mixtures  of  several  compounds  These  are  homogeneous  mixtures 
of  two  or  more  substances  that  crystallize  with  the  same  sym- 
metry, and,  consequently,  that  may  crystallize  together  Their 
physical  properties  are  continuous  functions  of  their  chemical  com- 
positions. Other  minerals  are  apparently  solid  solutions  in  one  an- 
other of  simple  crystallizable  salts,  of  gels,  of  gels  and  salts,  and  of 
gels  and  adsorbed  substances  Among  these  are  some  of  the  commoner 

Determination  of  Mineral  Composition. — Since  the  properties 
of  minerals  are  functions  of  their  chemical  compositions,  it  is  important 
that  their  compositions  be  known  as  accurately  as  possible.  It  is 
necessary  in  the  first  place  that  pure  material  may  be  secured  for  study 
Pure  material  is  most  easily  secured  by  making  use  of  the  differences 
in  density  exhibited  by  different  compounds  The  mineral  to  be  studied 
is  pounded  to  a  powder,  sifted  through  a  bolting  doth  sieve  and  shaken 
up  with  one  of  the  heavy  solutions  employed  in  determining  specific 
gravities.  When  the  solution  is  brought  to  the  same  density  as  that 
of  the  mineral  under  investigation  all  material  of  a  higher  specific  gravity 
will  sink.  The  material  with  a  density  lower  than  that  of  the  solu- 
tion will  rise  to  the  surface  Material  with  a  specific  gravity  identical 
with  that  of  the  solution  will  be  suspended  in  it  If  the  mixing  is  done 
in  a  separating  funnel  of  the  proper  type,  the  materials  may  be  drawn 
off  into  beakers  in  the  order  of  their  densities,  and  thus  the  pure  mineral 
may  be  separated  from  the  impurities  that  were  originally  incorporated 
with  it.  After  the  purity  of  the  substance  is  assured  by  examination 
under  the  microscope,  it  is  ready  for  analysis 

The  composition  of  the  purified  material  is  determined  by  the 
ordinary  methods  of  chemistry  known  as  analysis  and  synthesis. 

In  analysis  the  compound  is  broken  into  its  constituent  parts  and 
these  are  weighed,  or  it  is  decomposed  and  its  constituents  are  trans- 


formed  into  known  compounds  which  are  weighed  From  the  weights 
thus  obtained  the  proportions  of  the  components  m  the  original  sub- 
stance may  be  easily  calculated  if  the  weight  of  the  original  substance 
be  known 

In  synthesis  the  compound  is  built  up  from  known  elements  or 

If  the  mineral  caicite  (CaCOs)  is  decomposed  by  heat  into  lime 
(CaO)  and  carbonic  acid  gas  (CCte),  or  if  its  components  are  trans- 
formed into  the  known  compounds  CaSCU  and  KaCOj,  the  process  is 
analysis  If  the  known  substance  CCfe  is  allowed  to  act  upon  the 
known  substance  CaO  and  the  resulting  product  is  a  substance  possess- 
ing all  the  properties  of  caicite,  the  process  is  synthesis. 

Analytical  Methods.— The  analytical  methods  made  use  of  in 
mineralogy  are  (i)  the  ordinary  wet  methods  of  chemical  analysis, 
(2)  the  dry  methods  of  blowpipe  analysis,  in  which  the  mineral  is 
treated  before  the  blowpipe  without  the  use  of  liquid  reagents  except 
to  a  very  subordinate  degree,  and  (3)  microchemical  methods,  per- 
formed on  the  stage  of  a  compound  microscope. 

Blowpipe  and  microchemical  analyses  are  made  use  of  principally 
for  the  identification  of  minerals  By  their  aid  the  nature  of  the  atoms 
m  a  compound  may  easily  be  learned,  but  the  proportions  in  which 
these  atoms  are  combined  is  determined  only  with  the  greatest  difficulty. 
The  methods  are  mainly  qualitative 

Wet  Analysis.— For  exact  determinations  of  composition  the  wet 
methods  of  chemistry  are  usually  employed,  since  these  are  the  most 
accurate  ones  They  are  identical  with  the  methods  described  in 
manuals  of  quantitative  analysis,  and  therefore  require  no  detailed 
discussion  here  They  are  well  illustrated  by  Prof  Tschermak  as 
follows.  If  734  mg.  of  the  mineral  goethite  (in  which  qualitative  tests 
show  the  presence  of  iron  oxide  and  water)  are  roasted  in  a  glass  tube, 
water  is  given  off  This  when  caught  and  condensed  m  a  second  tube 
containing  dry  calcium  chloride  increases  the  weight  of  this  second 
tube  by  75  mg  The  residue  of  the  mineral  left  in  the  first  tube  now 
weighs  about  660  mg  An  examination  of  this  residue  shows  it  to  con- 
sist exclusively  of  the  iron  oxide  (FejjOs)  Since  only  iron  oxide  and 
water  are  present  in  goethite  the  sum  of  these  two  constituents  ought  to 
equal  the  original  weight  of  the  mineral  before  roasting  But  660+75  * 
—  73SJ  whereas  the  original  weight  was  734  The  difference  i  mg.  is| 
due  to  unavoidable  errors  of  manipulation.  As  it  is  very  small  it  may" 
be  neglected  in  our  calculations 

The  results  of  the  analysis  are  generally  expressed  in  percentages. 


which  are  obtained  by  dividing  the  weights  of  the  different  constituents 
by  the  weight  of  the  original  substance 

Thus:  660-  734=  89  92  per  cent  Fe20s 

75"~734=  10  22  per  cent  EfeO 

Total          100 14 

The  usual  methods  of  analysis  are,  however,  more  indirect  than  this, 
the  components  of  the  substance  to  be  analyzed  being  first  transformed 
into  known  compounds  and  then  weighed  For  instance,  common  salt 
is  known  by  qualitative  tests  to  contain  only  Na  and  CL  If  345  mg. 
of  the  pure  salt  be  dissolved  in  water  and  the  solution  be  treated  with 
silver  nitrate  under  proper  conditions  a  precipitate  of  silver  chloride 
is  formed  so  long  as  any  sodium  chloride  remains  in  the  solution.  The 
silver  chloride  is  separated  from  the  solution  by  filtration  It  contains 
all  the  chloride  present  m  the  345  mg  of  salt  After  drying,  its  weight 
is  determined  to  be  840  mg  The  solution  from  which  the  silver  chloride 
was  separated  contains  all  the  sodium  that  was  originally  present  in 
the  salt,  but  now  it  is  in  combination  with  nitric  acid  It  contains 
also  any  excess  of  silver  nitrate  that  was  added  to  precipitate  the  chlorine 

NaCl  +  AgNOs  -  AgCl  +  NaN03 

salt  reagent        precipitate         filtrate 

The  filtrate  is  now  treated  with  hydrochloric  acid  to  precipitate 
the  excess  silver  The  silver  chloride  precipitate  is  removed  by  filtra- 
tion, leaving  a  solution  containing  sodium  salts  of  nitric  and  hydro- 
chloric acids  besides  some  free  acid  of  each  kind.  Sulphuric  acid  is 
now  added  and  the  whole  solution  is  evaporated  to  dryness.  The  free 
acids  are  driven  off  by  the  heat  and  the  sodium  salts  are  transformed 
into  the  sulphate,  Na2S04  The  residue  consisting  exclusively  of  NaaSO* 
is  now  found  to  weigh  419  mg. 

The  345  mg  of  salt  have  yielded  840  mg.  of  AgCl  and  419  mg.  of 
NagS04  The  silver  chloride  is  known  to  contain  24  74  per  cent  of 
chlorine  and  the  sodium  sulphate  32  39  per  cent  of  sodium.  The  840 
mg  of  AgCl  contain  207.8  mg  of  chlorine,  and  the  419  mg  of 
contain  135  7  mg.  of  sodium.  Hence  345  mg  of  salt  yield 

207.8  mg.  or  60.23  per  cent  Cl, 
and  135  7  mg.  or  3934  per  cent  Na 

343.5  mg.        99.57  per  cent 


Records  of  Analyses. — The  composition  of  minerals  like  that  of 
other  chemical  compounds  is  determined  in  percentages  of  their  com- 
ponents and  is  recorded  as  parts  per  100  by  weight.  A  weighed  quantity 
of  themmeral  is  analy/ed,  the  products  of  the  analysis  are  weighed  and  the 
percentage  of  each  constituent  present  is  found  by  dividing  its  weight 
by  the  weight  of  the  original  substance,  as  has  already  been  indicated 

In  chemical  treatises  the  results  of  the  analyses  are  usually  recorded 
in  percentages  of  the  elements  present.  In  mineralogical  works  it  is 
more  common  to  write  the  percentage  composition  in  terms  of  the 
oxides  of  the  elements,  partly  because  the  old  analyses  are  recorded  in 
this  way  and  partly  because  certain  relations  between  the  mineral 
components  can  be  better  exhibited  by  comparison  of  the  oxides  than 
by  comparison  of  the  elements  present  in  them. 

The  record  of  the  analysis  of  a  magnestte  may  be  given  as. 

Mg=2835  per  cent, 

Fe=      34  per  cent, 

0=14  25  per  cent, 

0=5698  per  cent, 

Total =99,92  per  cent 

or  as 

MgO=47  25  per  cent, 
FeO=  43  per  cent, 
C02=S2  24  per  cent, 

Total =99  92  per  cent. 

Calculation  of  Formulas. — After  the  determination  of  the  per- 
centage composition  of  a  mineral,  the  next  step  is  to  represent  this 
composition  by  a  chemical  formula — a  symbol  which  indicates  the 
relative  number  of  elementary  atoms  in  the  mineral's  molecule,  instead 
of  the  number  of  parts  of  its  constituents  in  100  parts  of  its  sub- 

The  construction  of  a  formula  from  the  analytical  results  is  simple 
enough  in  principle,  but  in  practice  it  is  often  made  difficult  by  the 
fact  that  many  apparently  pure  substances  are  in  reality  composed  of 
several  distinct  compounds  so  intimately  mtercrystalhzed  that  it  is 
impossible  to  separate  them  In  the  simplest  cases  the  formula  is 
derived  directly  from  the  results  of  the  analyses  by  a  mere  process  of 

The  atomic  weights  of  the  chemical  elements  are  the  relative  weights 
of  the  smallest  quantities  that  may  enter  into  chemical  combination  with 
one  another,  measured  in  terms  of  the  atomic  weight  of  hydrogen  which 
is  taken  as  unity,  or  of  oxygen  taken  as  16.  Thus  the  atomic  weights 
of  nitrogen  and  oxygen  are  approximately  14  and  16  respectively,  i.e., 
the  smallest  quantities  of  nitrogen  and  oxygen  that  can  enter  into  com- 
bination with  each  other  and  with  hydrogen  are  in  the  ratio  of  the 





At  Weight 

Element                            Symbol 

At.  Weight 



27  i 



96  o 



120   2 



144  3 






20  2 



74  96 



58  68 



137  37 



222  4 



208  o 



14  oi 



II   0 



190  9 



79  92 



16  o 



112  40 



106  7 



132  81 



31  04 



40  07 



195   2 



12   OOS 



39  10 



140   25 






35  46 



226  o 



52  0 



102  9 



58  97 



85  45 



93  5 



101  7 



63  57 






162  5 

Scandium  . 


44  i 



167  7 



79  2 



152  o 



28  3 



19  o 



107  88 



157  3 



23  o 



69  9 






72  5 



32  06 



9  i 



181  5 



197  2 



127  5 



4  oo 



159  2 



163  5 



204  o 



i  008 



232  4 



114  8 



168  5 

Iodine.   .  . 


126  92 



118  7 

Indium.  . 


193  i 






55  85 



184  o 



82  92 



238  2 



139  o 



51  06 

Lead       . 


207  20 



130  2 



6  94 

Ytterbium  (Neoytterbium) 


173  5 




Yttrium,  . 



Magnesium.  .. 


24  32 

Zinc      . 


65  37 

Manganese.   . 


54  93 

Zirconium  •  » 


90  6 




values  14  1 6  :  i  l  The  quantities  that  possess  these  relative  weights 
are  known  as  atoms  Often  the  apparent  ratios  ot  the  elements  in 
combination  are  different  from  the  uitios  between  their  atomic  weights, 
but  this  is  always  due  to  the  fact  that  one  or  the  other  of  the  elements 
is  present  in  more  than  its  smallest  possible  quantity,  i  e  ,  in  a  greater 
amount  than  is  represented  by  a  single  atom  For  instance,  there  are 
several  compounds  of  oxygen  and  nitrogen  known,  in  which  the  weight 
relations  between  the  two  elements  may  be  represented  by  the  follow- 
ing figures  14  :  8,  14  :  16,  14  •  24,  14  :  32,  and  14  :  40  If  the 
second  of  these  compounds  consists  of  one  atom  each  of  nitrogen  and 
oxygen,  and  these  are  the  smallest  quantities  of  the  elements  that 
can  exist  in  combination,  the  several  compounds  must  be  made  up  thus 

14  :  8  14  .  16  14  .  24  14  :  32  14  *  40 

N2O  NO  N203  N02  N205 

for  N  can  exist  only  in  quantities  that  weigh  14,  28,  42  times  as  much 
as  the  smallest  quantity  of  hydrogen  present  in  any  compound,  i  e  , 
the  single  atom,  and  0  in  quantities  of  16,  32,  48,  etc  ,  times  the  weight 
of  the  single  hydrogen  atom  In  order  that  even  multiples  of  14  and 
1 6  shall  exist  in  the  ratios  given  above,  their  terms  must  be  multi- 
plied by  quantities  that  will  yield  the  following  results. 

28  .  1 6  14  :  16  28    48  14    32  28  :  80 

which  are  the  weights  respectively  of  the  numbers  of  atoms  lepresented 
in  the  above  formulas 

If,  then,  the  elements  combine  in  the  ratio  of  their  atomic  weights, 
or  in  some  multiple  of  this  ratio,  the  figures  obtained  by  analysis  must 
be  in  one  of  these  ratios,  and  consequently  they  furnish  the  data  from 
which  the  formula  of  the  substance  analyzed  may  be  deduced  In 
gold  chloride,  for  example,  analysis  shows  the  presence  of  64  87  per  cent 
Au  and  35  13  per  cent  Cl,  i  e  ,  the  gold  and  the  chlorine  are  united  in 

the  ratio  of  64.87  ;  35  13  or  -i-I.    The  combining  ratio  of  single 

tjj     «5 

atoms  of  gold  and  of  chlorine  is,  however,  196  7  •  35  5,  or  -2—Z      £Vi- 

oo  5 
dently  in  gold  chloride  the  ratio  of  gold  to  chlorine  is  only  one-third 

as  great  as  is  the  ratio  between  the  atomic  weights  of  these  elements, 
or  the  ratio  of  the  chlorine  to  the  gold  three  times  as  great.  Hence 

1  The  atomic  weight  of  hydrogen  is  more  accurately  i  008,  when  that  of  oxygen 
is  taken  as  16 



there  must  be  three  times  as  much  chlorine  in  gold  chloride  as  would 
be  represented  by  a  single  atom  of  chlorine,  or  there  must  be  three 
atoms  of  chlorine  in  the  compound,  for  we  cannot  imagine  a  quantity 
of  gold  present  which  is  equivalent  to  one-third  of  an  atom  of  gold 
Gold  chloride  is  therefore  AuCls 

We  can  now  prove  our  conclusion  by  calculation  One  atom  of 
gold  and  three  atoms  of  chlorine  ought  to  combine  in  the  ratio  of 
1967:1065  (le,  355X3)  If  our  conclusion  is  correct,  and  the 
gold  chloride  analyzed  is  AuCls,  then  the  quantities  of  gold  and  of 
chlorine  yielded  by  the  analysis  should  be  in  this  ratio  The  figures 
obtained  are  in  the  ratio  of  64  87  :  35  13  Multiplying  both  terms  of 
this  ratio  by  3  031  we  obtain  196  62  .  106  5,  which  is  approximately 
the  ratio  expected. 

In  practice,  the  same  result  as  that  outlined  above  is  reached  by 
dividing  the  results  of  analyses  by  the  atomic  weights  of  the  various 
elements  or  groups  of  elements  concerned  The  quotients  represent  the 
proportional  numbers  of  the  elements  or  groups  present.  If  the  small- 
est quotient  is  assumed  as  unity,  the  ratios  existing  between  this  and 
the  other  quotients  indicate  the  number  of  atoms  or  groups  of 
atoms  represented  by  the  latter. 


Gold  Chloride         Result  of  Analysis  Atomic  Weights          Quotients 

Au  =  64  87  per  cent   —   196  7  =   3298  = 
Cl   *  35  13  35  5  -   9896  = 

Tin  Chloride 


45  26  per  cent      -      117  4     =         384 
54  74  35  5      =      *  542 




4  04 

The  formula  of  the  gold  chloride  is  AuCls,  and  of  the  tin  chloride, 

Magnesium  carbonate  on  analysis  may  yield:  C=  14.26,  Mg=  28  37; 
Fe=.34,  0=5703,  or,  if  recorded  m  the  form  of  oxides:  002=52.24, 
MgO=47  25,  FeO=  43  From  either  of  these  results  the  formula  is 
easily  obtained  by  the  method  described. 

C=i4  26—11  97=1 188=1  009, 

Mg=  28  37- 23.94=  i  186=1.000, 

Fe~     .34-5588=  .006=  .006, 

0=57.03-15  96=3  573=3-°i2, 


MgCOs,  if  we  neglect  the  small 
quantity  of  iron  present 


From  the  second  set  of  figures  we  have* 

0)2=5224-4389=1  19  =  1,    ]  or> 

MgO=47  25— 3990=1  184=1,  r  MgO  C02,    which    is    the  same  as 
FeO=      43—7184=    006,        J     MgCOs,  written  in  a  different  way 

All  formulas  are  derived  by  methods  like  these,  but  in  many  cases 
the  processes  are  made  more  difficult  by  the  impossibility  of  deciding 
positively  whether  those  substances  that  are  present  in  small  quantities 
are  present  as  impurities  or  whether  they  exist  as  essential  parts  of 
the  compound 

Formulas  of  Substances  Containing  Two  or  More  Metallic 
Elements  or  Acid  Groups. — In  the  illustration  given  above  the  com- 
pounds consist  of  but  one  kind  of  metallic  element  combined  with  one 
kind  of  acid  Often  in  the  case  of  minerals  there  are  present  two  or 
more  metallic  elements,  and  less  commonly  several  acid  groups.  When 
two  metals  are  present  in  definite  atomic  proportions  the  formula  is 
written  in  the  usual  manner,  as  CaMg(COs)2  for  the  mineral  dolomite, 
in  which  calcium  and  magnesium  are  present  in  the  ratio  of  one  atom 
of  each  to  two  parts  of  the  acid  group  COa.  Very  often,  and  perhaps  in 
the  majority  of  cases,  when  two  or  more  metallic  elements  are  present 
in  different  specimens  of  a  mineral  they  are  not  found  always  in  the 
same  proportion — the  mineral  may  consist  of  isomorphic  mixtures 
of  several  substances  For  instance,  many  calcium-magnesium  car- 
bonates are  known  in  which  the  ratio  of  calcium  to  magnesium  present 
is  not  as  i  atom  to  i  atom,  but  in  which  this  ratio  is  as  2  atoms 
to  i  atom,  3  atoms  to  2  atoms,  or  a  ratio  which  would  have  to  be 
represented  by  irrational  figures  like  2  7236  atoms  to  i  5973  atoms 
Each  one  of  these  compounds  properly  requires  a  separate  formula, 
as  aCaCOa+MgCOs,  3CaC03+2MgCO3,  etc  ,  but  practically  the  entire 
series  of  compounds  is  represented  by  a  single  symbol,  thus  (Ca  Mg)  COs, 
indicating  that  in  the  series  we  have  to  do  with  mixtures  of  carbonates 
of  calcium  and  magnesium,  or  with  complex  molecules  containing  in 
different  instances  different  proportions  of  the  two  carbonates.  For 
greater  defimteness  the  symbol  of  the  characteristic  element  of  the 
substance  which  is  in  largest  quantity  in  the  compound  is  usually  written 
first,  as  (Ca  Mg)COs,  when  calcium  carbonate  is  m  excess,  or 
(Mg  Ca)COs  when  pnagnesmm  carbonate  predominates  If  still  greater 
defimteness  is  desired  small  figures  are  placed  below  the  symbols  of  the 
elements  concerned,  as  (Ca2  Mgi)COs  or  (Ca3  Mg2)C03,  to  indicate 
the  respective  proportions  present.  (Ca2  Mgi)COs  signifies  that  the 


mineral  thus  represented  contains  calcium   and  magnesium  in   the 
ratio  of  2  atoms  of  the  former  to  i  of  the  latter 

Compounds  Containing  Water.— Often  salts  that  separate  from 
aqueous  solutions  combine  with  certain  definite  proportions  of  water 
Sometimes  this  water  combines  with  the  anhydrous  portion  of  the  com- 
pound to  form  a  double  salt,  as  MgSO4+7H20,  or  MgS04  7H20 
At  other  times  a  portion  of  the  water,  in  the  form  of  the  group  (OH), 
called  the  hydroxyl  group,  occupies  the  place  usually  occupied  by 
a  metallic  element,  and,  occasionally,  that  usually  occupied  b>  an 
acid  group,  or  by  oxygen,  as  in  Mg(OH)2 

Water  of  Crystallization.— Double  salts  composed  of  an  anhydrous 
portion  combined  with  water  are  usually  well  crystallized  Although 
the  water  appears  in  many  cases  to  be  but  loosely  combined  with  the 
remainder  of  the  compound  it  is  an  essential  part  of  its  crystal  particle, 
for  by  the  loss  of  even  a  portion  of  it  the  crystal  system  of  the  compound 
is  often  changed  Water  in  this  form  is  known  as  water  of  crystalliza- 
tion, and  the  compounds  are  designated  hydrates 

The  magnesium  sulphate  MgSO*  7HaO  forms  orthorhombic  crystals 
By  evaporation  of  a  hot  solution  of  this  substance  the  sulphate 
MgSO4  6H20  separates  as  monochmc  crystals. 

Gypsum  is  CaSOi  2H2O  Its  crystallization  is  monoclinic  When 
heated  to  200°  it  passes  into  the  anhydrous  orthorhombic  mineral 
anhydrite,  CaS04 

Water  of  crystallization  may  frequently  be  driven  from  the  com- 
pound in  which  it  exists  by  continued  heating  at  a  comparatively  low 
temperature.  It  is  usually  given  off  gradually — an  increase  in  the  tem- 
perature causing  an  increase  in  the  quantity  of  water  released  until 
finally  the  last  trace  disappears  In  many  instances  such  a  very  high 
temperature  is  required  to  drive  off  the  last  traces  of  the  water  that  it 
would  appear  that  some  of  it  is  held  m  combination  in  a  different 
manner  from  that  in  which  the  remainder  is  held  Indeed,  it  is  not  at 
all  certain  that  double  salts  containing  water  of  crystallization  are 
different  in  any  essential  respect  from  ordinary  atomic  molecules  in 
which  hydrogen  and  oxygen  are  present  in  atomic  form. 

Combined  Water.— Water  of  crystallization  is  thought  of  as 
existing  in  the  compound  as  water  because  of  the  ease  with  which  it 
can  be  driven  off  Compounds  in  which  the  hydroxyl  group  is  present 
yield  water  only  upon  being  heated  to  comparatively  high  temperatures 
In  them  the  elements  of  water  are  present,  but  not  united  as  water. 
When  freed  from  their  combinations  with  the  other  constituents  of  the 
compound  by  heat  they  unite  to  form  water  Because  its  elements 


are  thought  of  as  closely  combined  with  the  other  elements  in  the 
molecule,  this  kind  of  water  is  often  distinguished  from  water  of  crystal- 
lization by  the  term  combined  water. 

Bructte  (Mg(OH)2)  and  malachite  (Cu2(OH)2C03)  are  minerals 
containing  the  elements  of  water  When  heated  they  yield  water 
according  to  the  reactions  Mg(OH)2  =  MgO+H2O  and  Cu2(OH)2COs 
=  CuO+CuC03+H20. 

Combined  water  is  not  only  more  difficult  to  separate  from  its  com- 
bination than  is  water  of  crystallization,  but  when  the  combination 
is  broken  the  chemical  character  of  the  original  substance  is  radically 
changed,  as  may  be  seen  from  the  reactions  above  indicated.  More- 
over, combined  water  is  given  off  suddenly,  at  a  certain  minimum 
temperature,  and  not  gradually  as  in  the  case  of  water  of  crystal- 

Blowpipe  Analysis. — Although  blowpipe  analysis  serves  merely  to 
identify  the  chemical  components  of  minerals,  it  is  a  most  important 
aid  to  mineralogists  in  their  practical  work 

Nearly  all  minerals  may  be  recognized  with  a  close  degree  of  accu- 
racy by  their  morphological  and  physical  properties  To  distinguish 
between  several  minerals  that  are  nearly  alike  in  these  characteristics, 
however,  the  determination  of  composition  is  often  important  In" 
cases  of  this  kind  a  single  test  made  with  the  blowpipe  will  frequently 
give  the  desired  information  as  to  the  nature  of  some  one  or  more  of 
the  chemical  elements  present,  and  thus  in  a  few  moments  the  mmeial 
may  be  identified  beyond  mistake 

The  apparatus  necessary  to  perform  blowpipe  analysis  is  very 
simple  and  the  number  of  pieces  few  These,  together  with  all  the 
reagents  in  sufficient  quantity  to  determine  the  composition  of  hundreds 
of  minerals,  may  be  packed  into  a  box  no  larger  than  a  common  lunch 
box  (See  pp  467-470) 

For  more  refined  work  than  the  mere  testing  of  minerals  a  larger 
collection  of  both  apparatus  and  reagents  is  necessary,  but  it  no  case 
is  the  quantity  of  material  consumed  in  blowpipe  analysis  as  great  as 
when  wet  methods  of  analysis  are  used 

Principles  Underlying  Blowpipe  Analysis.— The  principal  phe- 
nomena that  are  the  basis  of  blowpipe  work  are  the  simple  ones  known 
in  chemistry  as  volatilization,  reduction,  oxidation,  and  solution 

For  volatilization  experiments  charcoal  sticks  and  glass  tubes  are 
used  A  blowpipe  serves  to  direct  a  hot  blast  upon  the  assay.  The 
volatilized  products  collect  on  the  cool  parts  of  the  charcoal  which 
they  coat  with  a  characteristic  color,  or  upon  the  cooler  portions  of 


tlie  glass  tubes  The  sublimates  that  collect  in  the  tubes  may  be  tested 
with  reagents  or  examined  under  the  microscope 

Some  volatile  substances  impart  a  distinct  and  characteristic  color 
to  an  otherwise  colorless  flame  These  may  be  tested  in  the  direct  flame 
of  the  blowpipe 

Oxidation  and  reduction  experiments  are  usually  performed  either 
on  charcoal  or  in  glass  tubes  Oxidations  are  effected  in  open  tubes 
and  reductions  in  those  closed  at  one  end  The  products  of  the  oxida- 
tion or  of  the  reduction  are  studied  and  from  their  characteristics  the 
nature  of  the  original  substance  is  inferred 

The  solution  of  bodies  to  be  tested  is  often  made  in  the  usual  man- 
ner, i.e ,  by  treatmg  them  with  liquid  reagents,  but  more  frequently 
it  is  accomplished  by  fusion  of  a  small  quantity  of  the  body  with  borax 
(Na2B407  ioH20)  or  microcosmic  salt  ((NH4)NaHPO4  4H2Q).  The 
molten  reagent  dissolves  a  portion  of  the  substance  to  be  tested  and  in 
many  cases  forms  with  it  a  colored  mass  From  the  color  of  the  mass 
the  nature  of  the  coloring  matter  may  be  learned. 

Although  the  underlying  principles  of  blowpipe  analysis  are  simple 
the  reactions  that  take  place  between  the  reagents  and  the  assay  are 
often  very  complex. 

More  explicit  details  of  the  operations  of  qualitative  blowpipe 
analysis  are  given  in  Part  III 

Microchemical  Analysis. — The  processes  of  microchemical  analysis 
are  limited  in  their  application  to  the  detection  of  a  single  element  or, 
at  most,  of  a  very  few  elements  in  small  quantities  of  minerals.  They 
are  employed  mainly  in  deciding  upon  the  composition  of  a  substance 
whose  nature  is  suspected 

The  principle  at  the  basis  of  all  microchemical  methods  is  the  manu- 
facture of  crystallized  precipitates  by  treatment  of  the  mineral  under 
investigation  with  some  reagent,  and  the  identification  of  these  pre- 
cipitates through  their  optical  and  morphological  properties. 

In  practice,  a  small  particle  of  the  mineral  the  nature  of  which  it 
is  desired  to  know  is  placed  on  a  small  glass  plate,  which  may  be  covered 
with  a  thin  film  of  Canada  balsam  to  prevent  corrosion,  and  is 
moistened  with  a  drop  or  two  of  some  reagent  that  will  decompose 
it  The  solution  thus  formed  is  slowly  evaporated  by  exposure  to  the 
air  The  plate  is  then  placed  beneath  the  objective  of  a  microscope 
and  the  crystals  formed  during  the  evaporation  are  investigated  Or, 
after  a  solution  of  the  assay  is  obtained  there  is  added  a  small  quantity 
of  some  reagent  and  the  resulting  precipitate  is  studied  under  the 
microscope.  By  their  shapes  and  optical  properties  the  nature  of  the 


FIG  i  — Sodium  Fluosilicate  Crystals     Magnified  72  diam     (After  Rosenbusch ) 

FIG  2  —Potassium  Fluosihcate  Crystals     Magnified  140  diam,    (After  Rosenbusch ) 


crystals  produced  is  determined,  and  in  this  way  the  nature  of  the  con- 
stituents they  have  obtained  from  the  mineral  particles  is  discovered 

A  large  number  of  reagents  ha\  e  been  used  m  microchemical  tests 
each  of  which  is  best  suited  to  some  particular  condition  The  most 
generally  useful  one  is  hydrofluosihcic  acid  (H2SiFb).  If  small  frag- 
ments of  albite  and  of  orthoclase  are  placed  on  separate  glass  slips,  such 
as  are  used  for  mounting  microscopic  objects,  and  each  is  treated  with 
a  drop  of  this  reagent  and  then  allowed  to  remain  in  contact  with  the 
air  lor  a  few  minutes  until  the  solutions  begin  to  evaporate,  those 
portions  of  the  solutions  remaining  will  be  discovered  to  be  filled  with 
little  crystals  The  crystals  in  the  solution  surrounding  the  albite  are 
hexagonal  m  habit  (Fig  i),  while  those  in  the  solution  surrounding 
the  orthoclase  are  cubes,  octahedrons  or  combinations  of  forms  belonging 
to  the  isometric  system  (Fig  2).  The  former  are  crystals  of  sodium 
fluosihcate  and  the  latter  crystals  of  the  corresponding  potassium  salt 
The  albite,  consequently,  is  a  sodium  compound  and  the  orthoclase  a 
compound  of  potassium  In  similar  manner,  by  means  of  this  or  of 
other  reagents  the  constituents  of  many  minerals  may  be  easily  detected 
The  method,  however,  is  made  use  of  only  in  special  cases,  when  for 
some  reason  or  other  analytical  methods  are  not  applicable 

Synthesis. — Synthesis  is  the  opposite  of  analysis.  By  the  analytical 
processes  compounds  are  torn  apart,  or  broken  down,  whereas  by  syn- 
thetical operations  they  are  put  together  or  built  up  Synthetic  methods 
are  employed  principally  in  the  study  of  the  constitution  of  minerals 
and  of  their  mode  of  formation,  and  in  the  investigation  of  the  condi- 
tions that  determine  the  different  crystal  habits  of  the  same  mineral 
The  products  of  synthetic  reactions  are  often  spoken  of  as  artificial 
minerals  because  made  through  man's  agency  In  many  instances 
these  artificial  minerals  are  identical  in  every  sense  with  natural  minerals 
Consequently,  they  may  often  serve  as  material  for  study,  when  the 
quantity  of  the  natural  mineral  obtainable  is  too  small  for  the  purpose 

Classification  of  Minerals. — Classification  is  the  grouping  of 
objects  or  phenomena  in  such  a  manner  as  will  bring  together  those 
that  a're  related  or  that  are  similar  in  many  respects  and  will  separate 
those  that  are  different 

Since  minerals  are  chemical  compounds  whose  properties  depend  upon 
their  compositions,  then*  most  logical  classification  must  be  based  upon 
chemical  relationships.  But  their  morphological  and  physical  properties 
are  their  most  noticeable  features,  and  hence  these  should  also  be  taken 
into  account  in  any  classification  that  may  be  adopted.  Probably 
the  most  satisfactory  method  of  classifying  minerals  is  to  group  them, 


first,  in  accordance  with  their  chemical  relationships  and,  second,  m 
accordance  \\ith  their  morphological  and  physical  properties 

The  first  division  is  into  the  great  chemical  groups,  as,  for  instance, 
the  elements,  the  chlorides,  the  sulphides,  etc  The  second  division 
is  the  separation  of  these  great  groups  into  smaller  ones  comprising 
minerals  possessing  the  same  general  morphological  features  These 
smaller  groups  may  contain  only  a  single  mineral  or  they  may  contain 
a  large  number  of  closely  allied  ones  If  the  basis  of  the  subgroupmg 
is  manner  of  crystallization,  it  follows  that  the  members  of  subgroups 
containing  more  than  one  member  are  usually  isomorphous  compounds 
Thus  the  subdivisions  of  the  great  chemical  groups  are  single  minerals 
and  small  or  large  isomorphous  groups  of  minerals,  arranged  in  the 
order  in  which  their  metallic  elements  are  usually  discussed  in  treatises 
on  chemistry  For  example,  the  great  group  of  carbonates  embraces 
all  minerals  that  are  salts  of  carbonic  acid  (EfeCO'j)  This  great  group 
is  divided  into  smaller  groups  along  chemical  lines,  as  for  instance,  the 
normal  carbonates,  the  hydrous  carbonates,  the  basic  carbonates,  etc 
These  smaller  groups  are  finally  divided  into  subgroups  according  to 
their  morphological  properties — the  normal  salts,  for  example,  being 
divided  into  the  two  isomorphous  groups  known  as  the  calcite  and  the 
aragonite  groups,  and  a  third  group  comprising  but  a  single  mineral 

In  certain  specific  cases  some  other  classification  than  the  one 
outlined  above  may  be  desirable  For  instance,  in  books  written  for 
mining  students  it  is  often  found  that  a  classification  based  upon  the 
nature  of  the  metallic  constituent  is  of  more  interest  than  the  more 
strictly  scientific  one  outlined  above,  because  such  a  classification 
emphasizes  those  components  of  the  minerals  with  which  the  mining 
student  is  most  concerned  In  books  written  for  the  student  of  rocks, 
on  the  other  hand,  the  most  important  determinative  features  of  minerals 
are  their  morphological  characters,  hence  m  these  the  classification 
may  be  based  primarily  on  manner  of  crystallization 

In  the  present  volume  the  classification  first  outlined  is  used,  but 
because  such  a  small  proportion  of  the  known  minerals  are  discussed 
the  beauties  of  the  classification  are  not  as  apparent  as  they  would  be 
were  ail  described 


The  Origin  of  Minerals.— Minerals,  like  other  terrestrial  chemical 
compounds,  are  the  result  of  reactions  between  chemical  substances 
existing  upon  the  earth  When  they  are  the  direct  result  of  the  action 
of  elements  or  compounds  not  already  existing  as  minerals  they  are  said 
to  be  primary  products,  when  formed  by  the  action  of  chemical  agents 
upon  minerals  already  existing  they  are  often  spoken  of  as  secondary, 
though  this  distinction  of  terms  is  not  always  applied 

Quartz  (SiCb),  formed  by  the  cooling  of  a  molten  magma,  is  pnmar> , 
when  formed  by  the  action  of  water  upon  the  siliceous  constituents  of 
rocks  it  is  secondary 

The  Formation  of  Primary  Minerals  — Minerals  are  produced  in  a 
great  variety  of  ways  under  a  great  variety  of  conditions  Even  the 
same  mineral  may  be  produced  by  many  different  methods  The  more 
common  methods  by  which  primary  minerals  are  formed  are  precipita- 
tion from  a  gas  or  a  mixture  of  gases,  precipitation  from  solution,  the 
cooling  of  a  molten  magma,  and  abstraction  from  water  or  air  by  plants 
and  animals 

Deposits  from  Gases. — Emanations  of  gases  are  common  in  vol- 
canic districts  The  gases  escaping  from  volcanic  vents  are  mainly 
water  vapor,  hydrochloric  acid,  sulphur  dioxide,  sulphuretted  hydro- 
gen, ammonia  salts  and  carbon  dioxide,  besides  small  quantities  of  other 
gases  and  the  vapors  of  various  metallic  compounds  By  the  reactions 
of  these  with  one  another  or  with  the  oxygen  of  the  air,  sulphur,  salam- 
momac  (NHiCl)  and  other  substances  may  be  formed,  and  by  their 
reaction  upon  the  rocks  in  the  neighborhood  halite  (NaCl),  ferric  chlo- 
ride (FeCls),  hematite  (Fe20s)  and  many  other  compounds  may  be 

The  production  of  minerals  through  the  reactions  set  up  between 
various  gases  and  vapors  is  known  as  pneumatolysis  Their  separation 
from  the  gaseous  condition  is  known  as  sublimation  Minerals  formed 
by  sublimation  are  usually  deposited  as  small,  brilliant  crystals  on  the 
surfaces  of  rocks  or  upon  the  walls  of  cavities  and  crevices  in  them. 



The  reactions  by  %\hich  they  are  produced  are  often  quite  simple.  Thus 
the  reaction  between  sulphuretted  hydrogen  and  sulphur  dioxide  yields 
sulphur  (2H2S+S02  =  3S+2H20),  as  does  also  the  reaction  between  the 
first  named  gas  and  the  oxygen  of  the  atmosphere  (HjS+O  =  H2O+S) 
Ferric  chloride  may  be  produced  by  the  action  of  hot  hydrochloric 
acid  upon  some  iron-bearing  material  deep  within  the  earth's  in- 
terior This  being  volatile  at  high  temperatures  escapes  to  the  air 
as  a  gas  Here  it  may  react  with  water  vapor,  with  the  resulting  for- 
mation of  hematite  (2FeCl3+3H20=Fe203+6HCl)  By  the  action 
of  carbonic  acid  gas  upon  volatile  oxides,  carbonates  are  formed, 
(Fe203+2C02=2FeCOa+0)  In  other  cases,  however,  the  reactions 
are  very  complicated 

Precipitation  from  Solution. — Nearly  all  substances  are  soluble 
to  an  appreciable  degree  in  pure  water  An  increase  in  temperature 
usually  increases  the  quantity  of  the  substance  that  can  be  dissolved, 
as  does  also  an  increase  of  pressure  Moreover,  the  solubility  of  a 
salt  is  increased  on  the  addition  of  another  salt  containing  no  common 
ion,  and,  conversely,  is  diminished  in  the  presence  of  another  having  a 
common  ion  Thus,  gypsum  (CaS04  2H20)  is  sparingly  soluble  in 
water,  but  it  becomes  much  more  soluble  upon  the  addition  of  salt 
(NaCl)  On  the  other  hand,  salt  (NaCl)  is  much  less  soluble  in  water 
containing  a  little  magnesium  chloride  (MgClo)  than  it  is  in  pure  water. 

When  a  solvent  contains  a  maximum  amount  of  any  substance  that 
it  may  hold  under  a  given  set  of  conditions  the  solution  is  said  to  be 
saturated  From  a  saturated  solution  under  ordinary  conditions 
precipitation  results  Upon  the  evaporation  of  the  solvent,  the  lowering 
of  its  temperature  or  of  the  pressure  under  which  it  exists,  or  the  addi- 
tion to  the  solution  of  a  substance  containing  an  ion  already  in  the 
solution.  Of  course,  the  addition  of  a  substance  which  will  react  with 
the  solution  and  produce  a  compound  insoluble  m  it  will  also  cause 

The  following  table  contains  the  results  of  various  experiments  on 
the  solubility  of  some  common  minerals 

(The  results  are  given  in  parts  by  weight) 

Halite  (NaCl),  at  7°  35  68  Calcitc  (CaCO,),  in  the 
Fluonte  (CaF2),  at  15^°                  0037  cold  002 

Gypsum  (CaS04  2H20),ati5°        250  Strontiamte   (SrCO,)  in 
Anhydrite  (CaS04),  in  the  cold        00025  the  cold  00555 

Celestite  (SrS04),  at  14°  015  Magnetite  (Fte()4)  00035 



(When  treated  30  to  32  da\s) 

Galena  (PbS)  179  Chalcop>nte  CCuFeS2)  1669 

Stibmte  (Sb2S3)  5  01  Bouraomte  f(Pb  Cu)SbS3)      2  075 

Pynte  (FeS2)  2  99  Arsenopynte  (FeAsSj  i  5 

Sphalerite  (ZnS)  025 

So  many  substances  that  are  usually  regarded  as  insoluble  are  known 
to  be  dissoh  ed  under  conditions  of  high  temperature  and  pressure  that 
no  substance  is  behe\  ed  to  be  entirely  insoluble 

Po\\dered  apophylhte  ((HK)2Ca(Si03)2  H20),  which  is  a  silicate 
that  is  generally  regarded  as  insoluble  in  water,  is  dissoh  ed  sufficiently 
in  this  sohent  at  a  temperature  of  i8o°-iQO°  and  under  a  pressure  of 
10-12  atmospheres  to  }ield  crystals  of  the  same  substance  upon  cooling 

Water  containing  gases  or  traces  of  salts  is  usually  a  more  efficient 
dissolving  agent  than  pure  water  When  the  gases  are  lost,  or  the 
salts  are  decomposed  by  reactions  with  other  compounds,  precipitation 
may  ensue 



Gold  loses  i  23  per  cent  of  its  \\eight  when  treated  with  10  per  cent  soda 
solution  at  200° 

One  part  gypsum  (CaSO4  2H20)  dissolves  in  199  parts  of  saturated  NaCl 
solution  Only  4  part  dissolves  in  200  parts  pure  \\ater 

Pyt  lie  (FeSo)  loses  10  6  per  cent  of  its  mass  upon  boiling  for  a  long  time 
with  a  solution  of  Na2S  Under  the  same  circumstances  galena  loses  2  3 
per  cent 

One  of  the  commonest  of  the  gases  found  in  water  on  the  earth's 
surface  is  carbon  dioxide  This  is  an  active  agent  in  decomposing  sili- 
cates and  in  dissolving  carbonates,  so  that  water  m  which  it  is  dissolved 
is  usually  a  more  powerful  solvent  than  pure  water  Its  dissolving 
power  increases  with  the  pressure,  as  in  the  case  of  pure  water,  but 
diminishes  with  increasing  temperature  The  action  of  carbonated 
water  on  silicates  is  due  to  the  replacement  of  the  silicic  acid  by  carbonic 
acid  and  the  production  of  bicarbonates,  which  are  usually  more  soluble 
than  the  corresponding  carbonates  The  greater  solubility  of  carbon- 
ates, like  calcite,  in  carbonated  water  is  also  due  to  the  formation  of 
bicarbonates  For  example,  the  action  of  carbonated  water  upon  cal- 
cite (CaCOs)  is  as  follows 



Carbonated  water  is  more  effective  as  a  solvent  under  pressure 
because  of  the  inability  of  the  CCb  to  escape  under  this  condition  When 
pressure  is  removed  the  CCb  escapes,  or  evaporation  takes  place,  and  the 
reverse  reaction  occurs,  as 

CaH2(C03)2= CaC03+H20+CO2 

The  dissolving  effect  of  carbonated  water  upon  various  carbonates 
and  other  minerals  and  the  influence  of  pressure  and  temperature  upon 
the  solution  of  a  carbonate  are  indicated  in  the  three  tables  following 



(The  results  are  given  in  parts  by  weight) 

Calcite  (CaC03),  at  10°  10  o       Sidente  (FcCO,)  at  18°  7  2 

Dolomite  (CaMg(COs)2)  at  18°     3  i        Witherite  (BaCOj)  at  10°  170 

Magnesite  (MgCOs),  at  5°          13  i        Strontiamte  (SrCOi),  at  10°       12  o 


(When  treated  7  weeks) 

Adulana  (KAlSiaOs)  328  Apatite  (Ca«(F  CIXPCX).)        i  821 

Ohgoclase  Apatite  (Cafi(F  Cl)(POi)0         2  018 

(NaAlSi308+  CaAl(SiO)4)          533  Olivme  ((Mg  Fe)2Si04)  2111 

Hornblende  (complex  silicate)  i  536  Magnetite  (Fe304)          307  to  i  821 
Serpent]  ne  (KUMgsSi'Oo)            i  211 


(The  results  are  given  m  parts  per  10,000  by  weight) 

i  atmos  at  19°      2  579  parts       Temp    13  4°  under  i  atmos      2  845  parts 
32  3  730  29  3  2  105 

56  4  620  62  o  i  035 

75  5  120  82  o  400 

90  5  659  100  o  ooo 

Precipitation  from  Atmospheric  Water  —Rain  is  an  active  agent 
in  dissolving  mineral  matter  Since  it  absorbs  small  quantities  of  carbon 
dioxide,  sulphur  gases  and  other  substances  as  it  passes  through  the 
atmosphere  it  may  act  upon  many  compounds,  dissolving  some,  decom- 
posing others  and  forming  soluble  compounds  from  those  that  would 
otherwise  be  practically  insoluble  Moreover,  it  transports  the  dissolved 
materials  from  one  portion  of  the  crust  to  some  other  portion,  where, 
under  favorable  conditions,  they  may  be  precipitated  The  rain  water 
that  penetrates  the  earth's  crust,  dissolving  and  precipitating  in  its 



course  through  the  crust,  is  known  as  vadose  water  It  is  an  important 
agent  in  ore-formation,  since  it  may  collect  mineral  matter  from  a  great 
mass  of  rocks  and  precipitate  it  in  some  favorable  place,  thus  making 
ore  bodies 

Deposits  of  Springs. — Springs  are  the  openings  at  which  under- 
ground \\ater  escapes  to  the  earth's  surface  Much  of  the  water  flowing 
from  springs  is  the  meteoric  water  which  has  circulated  through  the 
crust  and  is  again  seeking  the  surface  In  its  course  through  the  crust  it 
dissolves  certain  materials  Where  it  reaches  the  surface  some  of  this 
material  may  be  dropped  in  consequence  of  (i)  evaporation  of  the  \\ater, 
or  (2)  the  escape  of  carbon  dioxide,  or  (3)  the  oxidation  of  some  of  its 
constituents  through  the  action  of  the  air,  or  (4)  the  cooling  of  the  water 
in  the  case  of  warm  or  hot  springs 

The  deposits  thus  formed  may  occur  as  thin  coatings  on  the  rocks 
over  which  the  spring  water  passes,  or  as  layers  in  the  bottom  of  the 
spring  and  the  stream  issuing  from  it  Among  the  commonest  minerals 
thus  deposited  are  calcite  (CaCOs),  aragomte  (CaCOs),  siderite  (FeCOs) 
and  other  carbonates,  gypsum  (CaSO-i  2H20),  pynte  (FeS2),  sulphur 
(S),  and  limonite  (Fe4O3(OH)6)  The  carbonates  are  deposited  largely 
in  consequence  of  the  escape  of  C02  from  the  water,  gypsum  in  conse- 
quence of  cooling,  and  limonite  and  sulphur  through  oxidation.  If  the 
water  contains  EkS,  this  reacts 
with  the  oxygen  and  a  deposit  _  4  j, 
of  sulphur  ensues  (compare 
P  18) 

When  the  precipitation  oc- 
curs m  cracks  or  fissures  in  the 
rocks  the  precipitated  matter 
may  partially  or  completely  fill 
the  fissure,  producing  a  vein,  or, 
the  precipitated  matter  may  fill 
an  irregular  cavern  forming  a 
bonanza  It  sometimes  covers 
the  walls  of  cavities  or  the  sur- 
faces of  minerals  already  exist- 
ing, giving  rise  to  a  druse  In 
other  cases  precipitation  may 
occur  while  the  solution  is  dripping  from  an  overhanging  surface, 
making  a  stalactite,  or  the  precipitate  may  fill  the  tiny  crevices  between 
grains  of  sand  cementing  the  loose  mass  into  a  compact  rock 

Mmerals  produced  by  precipitation  are  often  beautifully  crystallized. 

FIG  3  — Cross-section  of  Symmetrical  Vein 
(Aflts  Le  Neue  Foster  ) 

(a)  Decomposed  rock  ($)  Galena 

(6)  Quartz  crystals  (d)  Sidente 


At  other  times  they  form  groups  of  needles  yielding  globular  and  other 
imitative  shapes,  while  in  still  other  instances  they  occur  as  pulverulent 
or  amorphous  masses  The  fillings  of  veins  are  often  arranged  sym- 
metrically, similar  materials  occurring  on  opposite  sides  of  their  central 
planes  in  bands,  as  shown  in  the  figure  (Fig  3)  Some  important  ores 
have  been  concentrated  and  deposited  in  this  way 

Deposits  from  Hot  Springs.-— The  water  of  hot  springs  deposits  a 
greater  variety  of  minerals  than  that  of  cold  springs  Practically  all 
minerals  that  are  soluble  in  hot  water  or  in  hot  solutions  of  salts  are 
among  them  Among  those  of  economic  value  may  be  mentioned 
cinnabar  (HgS)  and  stibnite  (Sb2Ss) 

Deposits  from  the  Ocean  and  Lakes. — The  water  of  the  ocean  and 
of  many  lakes  is  rich  in  dissolved  salts.  That  of  lakes,  however,  is  often 
saturated  or  nearly  so,  while  that  of  the  ocean  is  not  near  the  saturation 
point.  Consequently,  while  many  lakes  may  deposit  mineral  sub- 
stances, the  ocean  does  not  do  so  except  under  peculiar  conditions  When 
a  portion  of  the  ocean  is  separated  from  the  mam  body  of  water,  it  may 
evaporate  and  leave  all  of  its  mineral  matter  behind  Lakes  may  also 
completely  evaporate  with  a  similar  result  In  each  case  the  deposits 
form  layers  or  beds  at  the  bottom  of  the  basin  in  which  the  water  was 

In  other  instances  the  water  brought  to  the  ocean  or  a  lake  may 
contain  substances  which  will  react  with  some  of  the  materials  already 
present  and  produce  an  insoluble  compound  which  will  be  precipi- 

Of  course,  the  nature  of  the  beds  thus  formed  will  depend  upon  the 
character  and  proportions  of  the  substances  that  were  in  the  water 
The  ocean  will  yield  practically  the  same  kinds  of  compounds  all  over 
the  world  and  the  beds  deposited  by  the  evaporation  of  ocean  water 
will  be  formed  in  nearly  the  same  succession  everywhere  In  the  case 
of  enclosed  bodies  of  water — like  lakes  or  seas — in  which  the  composi- 
tion of  the  water  may  differ,  the  deposits  formed  may  also  differ 

Many  of  the  deposits  formed  in  bodies  of  water  are  of  great  eco- 
nomic importance  and,  consequently,  are  extensively  worked  Prob- 
ably the  most  important  are  the  beds  of  salt  (NaCl)  and  of  gypsum 
(CaSO4  2H20),  although  borax  (Na2B407  ioH20)  was  foimerly 
obtained  in  large  quantity  from  the  deposits  of  some  of  the  lakes  in 
the  desert  portions  of  the  United  States 

In  the  following  table  are  given  the  results  of  analyses  of  water  of 
the  ocean  and  of  Great  Salt  Lake,  in  Utah,  calculated  on  the  assump- 
tion that  the  elements  are  combined  in  the  manner  indicated  m  the 



column  on  the  left     The  results  of  the  analyses  of  the  waters  of  a  few 
noted  lakes  are  given  in  the  succeeding  table 








(Parts  in  1000  of  Water) 

I  II 

27  3726  8  1163 

5921  1339 

3  3625  6115 

1  3229  9004 

2  2437  3  0855 














118  628 

14  908 

9  321 
5  363 


35  0433 

12  9427 

149  078 

I   Water  of  N  Atlantic  off  Norwegian  Coast     Anal>st,  C  Schmidt 
II   Average  of  Five  Analyses,  Caspian  Sea  at  depths  of  from  i  m   to  640  m 

Analyst,  C  Schmidt 
III    Great  Salt  Lake,  Utah     Analyst,  O  D  Alien 












Total  Solids 
(per  1000 
of  Water) 

Dead  Sea 
Lake  Beisk,  Siberia 
Qoodenough  Lake,  B  C 
Borax  Lake,  Cal 

64  49 
22  79 
7  64 
32  27 

1  45 



42  32 

7  OS 

41  41 
22  47 

15  75 
31  32 
36  17 
38  10 

3  24 
1  01 
6  65 
1  52 

4  09 

10  53 
1  86 


220  3 
104  7 
103  47 
76  56 

Deposits  from  Magmatic  Water. — Equally  important  in  depositing 
mineral  matter  is  the  water  that  escapes  from  cooling  lavas  and  other 
molten  magmas — designated  as  juvenile  water  All  molten  magmas 
existing  under  pressure,  i  e ,  at  some  distance  beneath  the  crust,  contain 
the  components  of  water,  which  escape  as  the  magma  cools  or  when  the 
pressure  diminishes,  whether  the  diminution  of  the  pressure  is  due  to 


the  escape  of  the  lava  to  the  surface  or  to  the  cracking  of  the  crust 
In  its  passage  to  the  surface  the  hot  water  carrying  dissolved  salts  pene- 
trates all  the  cracks  and  cavities  in  the  rocks  through  which  it  passes 
in  its  ascent  and  deposits  its  burden  of  material,  forming  veins  and  other 
types  of  deposits  Or,  its  components  may  decompose  the  materials 
with  which  it  comes  in  contact,  replacing  them  wholly  or  in  part  by  the 
substances  which  it  is  carrying  or  by  the  products  of  decomposition 

FIG.  4  —Cross-section  of  Vein  in  Green  Porphyry      The  vein  filling  is  chalcedonj 
The  white  splotches  are  feldspar  crystals     The  fairly  uniform  character  of  the 
rock  where  not  affected  by  the  vein  is  seen  on  the  right  side  of  the  picture     The 
rude  banding  parallel  to  the  vein  is  due  to  changes  that  have  proceeded  out- 
ward from  the  vein-mass  into  the  rock 

Since  in  many  cases  magmatic  water  contains  corrosive  gases,  such  as 
fluorine,  its  action  on  the  rocks  which  it  traverses  is  profound  A  tiny 
crack  in  the  rocks  may  be  gradually  widened  and  the  material  on  both 
sides  of  it  be  replaced  by  new  material,  thus  producing  a  vein  which 
is  sometimes  difficult  to  distinguish  from  a  vein  made  in  other  ways 
(Fig  4)  This  process  is  known  as  metasomatism,  which  is  one  kind  of 
metamorphism  It  is  an  important  means  of  producing  pseudomorphs 
and  bodies  of  mineral  matter  sufficiently  rich  in  metallic  contents  to 
constitute  ore-bodies 


Solidification  from  Molten  Magmas.— A  molten  magma,  such  as  a 
liquid  lava,  is  probably  a  solution  of  various  substances— mainly  sili- 
cates— in  one  another,  or  in  a  hot  solvent  Upon  cooling  or  upon  change 
of  conditions,  such  as  may  arise  from  loss  of  gas  or  water  or  from  reduc- 
tion of  pressure,  this  hot  solution  graduall}  deposits  some  of  its  con- 
stituents as  definite  chemical  compounds  Upon  further  cooling  other 
compounds  solidify  and  so  on,  until  finally,  if  the  rate  of  cooling  has  been 
slo\\,  the  entire  mass  may  separate  as  an  aggregate  of  minerals— such 
as  constitute  many  of  the  rocks,  as  granite  for  instance,  and  main  of  the 
lavas  If  the  cooling  has  been  rapid,  some  of  the  material  ma\  separate 
as  definite  minerals  \\hile  the  remainder  solidifies  as  a  homogeneous 
glass,  as  in  the  case  of  most  lavas  Sometimes  the  minerals  thus  formed 
are  bounded  by  crystal  planes,  but  usually  their  growth  has  been  so 
interfered  with  that  it  is  only  by  their  optical  properties  that  they  can 
be  recognized  as  crystalline  substances  The  nature  of  the  minerals 
that  separate  depends  upon  a  great  variety  of  conditions,  the  most 
important  of  which  is  the  chemical  composition  of  the  magma 

In  some  cases  the  minerals  separating  from  a  magma  tend  to  segre- 
gate m  some  limited  portion  of  its  mass  and  thus  produce  an  accumula- 
tion that  may  be  of  economic  value,  le,  the  magma  dijf a  entities 
Magnetite  (FesGO,  ilmenite  ((Fe  Ti)203),  pynte  (FeS2)  and  a  few  other 
minerals  are  sometimes  segregated  in  this  way  in  very  large  masses 

Metamorphic  Minerals  — Many  minerals  are  characteristic  of  rocks 
that  are  in  contact  with  others  that  were  once  molten  They  were 
formed  by  the  gases  and  hot  waters  given  off  from  the  magmas  before  they 
cooled  The  hot  solutions  with  their  charges  of  gas  and  salts  penetrated 
the  pores  of  the  surrounding  rock  and  deposited  in  them  some  of  their 
material  They  reacted  with  some  of  the  rock's  components,  producing 
new  compounds,  and  extracted  others,  leaving  pores  into  which  new 
supplies  of  gas  and  water  might  enter  In  some  cases  the  entire  body 
of  the  surrounding  rock  has  been  replaced  by  new  material  for  some 
distance  from  the  contact  Beyond  this  belt  of  most  profound  meta- 
morphism  are  other  belts  in  which  the  rock  is  less  altered,  until  finally  in 
the  outer  belt  is  the  unchanged  original  rock  Into  the  outer  contact 
belt  perhaps  only  gas  penetrated  and  the  changes  here  may  be  entirely 
pneumatolytic  Near  the  contact  the  changes  may  be  metasomatic 
Minerals  formed  by  these  processes  near  the  contact  of  igneous  masses 
are  frequently  referred  to  collectively  as  contact  minerals. 

In  other  cases  new  minerals  may  be  produced  in  rocks  in  consequence 
of  crushing  attended  by  heat  Hot  water  under  high  pressure 
greatly  facilitates  chemical  changes  A  part  of  the  materials  of  the 


crushed  rock  dissolves,  reactions  are  set  up  and  new  compounds  may 
be  formed  The  new  minerals  produced  are  more  stable  than  the 
original  ones  and  have  in  general  a  greater  density  and  consequently 
a  smaller  volume  The  type  of  metamorphism  that  produces  these 
effects  is  kno\\n  as  dynamic  metamot  phtsm 

Organic  Secretions.— The  transfer  of  mineral  substances  from  a 
state  of  solution  to  the  solid  condition  is  often  produced  through  the  aid 
of  organisms  Mollusca,  like  the  oyster,  clam,  etc ,  crustaceans,  like 
the  lobster  or  crab,  the  microscopic  animals  and  plants  known  as  pro- 

FIG  5  — Diorite  Dike  Cutting  Granite  Gneiss     Pelican  Tunnel,  Georgetown,  Colo. 
(After  Sptirr  and  Garry ) 

tozoans  and  algae  and  many  other  animals  and  vegetables  abstract 
mineral  matter  from  the  water  in  which  they  live  and  build  up  for  them- 
selves hard  parts  These  hard  parts,  usually  in  the  form  of  external 
shells,  are  composed  of  calcium  carbonate  (CaCOs),  either  as  calcite  or 
aragomte,  of  silica  (8102)  or  of  calcium  phosphate  Cas(P04)2.  Although 
not  commonly  regarded  as  minerals  these  substances  are  identical 
with  corresponding  substances  produced  by  inorganic  agencies  l 

Paragenesis.— It  is  evident  that  minerals  produced  in  the  same 

1  Plants  and  animals  upon  decaying  yield  organic  acids  which  may  attack  minerals 
already  existing  and  thus  give  nse  to  solutions  which  may  deposit  pynte  (FeSa), 
hmomte  (a  hydrated  iron  oxide)  or  some  other  metallic  compound  This  process, 
however,  is  properly  simply  a  phase  of  deposition  from  solutions 


\\ay  \\  ill  generally  be  found  together.    A  certain  association  of  minerals 
will   thus   characterize   deposits   from   magmas,    another   association 

FIG  6  — Vein  in  Griffith  Mine,  Georgetown   Colo ,  Showing  Two  Periods  of  Vein 
Deposition     (After  Spwr  and  Garry  ) 

gn  =  wall  rock  6  =  sphalerite  c  —  chalcopynte 

ff  =  comb  quartz  p  =  pynte  g  =  galena 

Balance^of  vein-filling  is  a  mixture  of  manganese-iron  carbonates 



It      \Z 

13      SH- 

FIG  7     Vein  Forming  Original  Ore-Body,  Butte,  Mont     (After  W.H  Weed) 

(i)  Fault  breccia,    (2)  ore,    (3)  altered  granite,    (4)  first-class  ore,   (5)  crushed  quartz  and 

bormte,  (6)  fault  clay,  (7)  solid  pyrite  and  bormte,  (8)  crushed  quartz  and  pynte,   (9)  solid 

enargite  ore  with  bormte,    (10)  banded  white  quartz  and  bormte,   (n)  white  quartz,  6  inches, 

(12)  solid  bormte,  (13)  solid  pynte  with  bormte  and  quartz  blotches,  (14)  bormte,  (15)  granite. 

those  precipitated  from  water,  another  those  produced  by  contact 
action,  etc     This  association  of  minerals  of  a  similar  origin  is  known 



as  their  paragenesis      From  a  study  of  their  relations  to  one  another  the 
order  of  their  deposition  may  usually  be  determined 

Occurrence. — The  manner  of  occurrence  of  mineral  substance  is 
extremely  varied,  as  may  be  judged  from  the  consideration  of  the  vari- 
ous ways  in  which  they  are  formed  Deposits  laid  down  in  water  occur 
in  beds  or  in  the  cement  uniting  grains  of  sand,  etc ,  such  as  the  beds 
of  salt  (NaCl)  or  gypsum  (CaSO*  2H20)  found  in  many  regions  Those 
produced  by  the  cooling  of  magmas  may  form  great  masses  of  rock 
such  as  granite,  \vhich  when  it  occurs  as  the  filling  of  cracks  in  other 
rocks  is  said  to  have  the  form  of  a  dike  (Fig  5)  Deposits  made  by 

water,  whether  meteoric  or  mag- 
matic  may  give  rise  to  veins,  which 
may  be  straight-walled  or  branch- 
ing, like  the  veins  of  quartz  (Si02) 
that  are  so  frequently  seen  cutting 
various  siliceous  rocks  When  the 
veins  aie  filled  by  meteoric  water 
they  often  have  a  comb-structure — 
the  filling  consisting  of  several  sub 
stances  arranged  in  definite  layers 
following  the  vein  walls  (see  p  21) 
If  the  composition  of  the  depositing 
solution,  whether  meteoric  or  mag- 
matic,  has  remained  constant  for  a 
long  time  the  vein  may  be  filled 
with  a  single  substance  It  its  com- 
position changed  during  the  time 
the  filling  was  in  progress  the  layers 
are  of  different  kinds  Further,  it 
deposition  continued  uninterruptedly 
the  layers  may  match  on  opposite 
sides  of  the  vein  and  the  succession 
may  be  the  same  from  walls  to  center  If,  however,  after  the  partial 
or  complete  filling  of  the  crack  it  was  reopened  and  the  new  crack  was 
filled,  the  new  vein  when  filled  would  be  unsymmetncal  if  the  new  crack 
occurred  to  one  side  of  the  center  of  the  original  vein  (Fig  6)  Repeated 
reopening  may  give  rise  to  a  vein  that  is  so  lacking  in  symmetry  that 
it  is  difficult  to  trace  the  succession  of  events  by  which  it  was  produced 
(Fig  7)  Veins  filled  by  magmatic  water  are  frequently  more  homo- 

Druses  (Fig  8)  arise  when  deposits  simply  coat  the  walls  of  fissures. 

FIG  8  —Druse  of  Smithsomte  (ZnCO3) 
on  Massive  Smithsomte 



In  many  cases  they  may  be  regarded  as  veins,  the  development  of  which 
has  been  arrested  and  never  completed  When  the  deposits  coat  the 
walls  of  hollows  within  rocks  they  are  known  as  geodes  (Fig  9)  Geodes 
are  common  in  limestones  and  other  easily  soluble  rocks  in  \*hich 
cavities  may  be  dissolved 

Gases  and  water  under  great  pressure  may  penetrate  the  micro- 
scopic pores  existing  in  all  rocks  and  there  deposit  material  which  may 
fill  the  pores  and  cement  the  rocks  If  the  deposited  material  is  metallic 
the  rocks  may  be  transformed  into  masses  sufficiently  rich  in  metallic 
matter  to  become  ore-bodies  A  body  of  this  kind  is  known  as  an 
impregnation  It  is  well  represented  by  some  of  the  low  grade  gold 
ores,  such  as  those  in  the  Black  Hills 

When  rocks  are  decomposed  bv  the  weather  they  are  broken  up 

FIG  9  —Geodes  Containing  Calcite  (CaCOs)  Crystals 

The  rains  wash  the  disintegrated  substance  into  streams  In  its  course 
downward  to  lakes  or  the  ocean,  the  heavier  fragments,  such  as  metallic 
particles,  may  settle  while  the  lighter  portions  are  carried  along 
Thus  the  heavy  parts  may  accumulate  in  the  stream  bottoms  These 
materials,  consisting  of  gold,  magnetite,  garnet,  pyrite  and  other  min- 
erals of  high  specific  gravity,  form  a  loose  deposit  m  the  stream  bed 
which  is  known  as  a  placer.  Gold  is  often  found  in  placer  deposits 
The  lighter  portions  may  be  carried  to  the  lake  or  sea  into  which  the 
streams  enter  and  may  accumulate  as  sand  on  beaches  and  on  the 
bottom  near  the  shores  as  gravel,  sand,  silt,  etc  Most  sand  consists 
principally  of  quartz,  but  many  sands  contain  also  grains  of  feldspar 
and  other  silicates,  and  sometimes  other  compounds 


Alteration  of  Minerals.— Minerals,  like  living  things,  are  constantly 
subject  to  change  Circulating  waters  may  dissolve  them  in  part, 
or  completely,  and  transport  their  material  to  a  distant  place,  there 
depositing  it  either  in  the  form  it  originally  possessed  or  in  some  new 
form  On  the  other  hand,  the  mineral  substance  may  be  decomposed 
into  several  compounds  some  of  which  may  be  carried  off,  while  others 
are  left  behind  Again,  the  material  remaining  behind  may  com- 
bine with  other  matter  held  in  the  water  causing  the  decomposition, 
and  may  form  with  it  a  new  mineral  or  a  number  of  different  minerals 
occupying  the  place  of  the  original  one  This  is  m  part  metasomatism 

The  atmosphere  may  also  act  as  a  decomposer  of  minerals  Through 
the  agency  of  its  oxygen  it  may  cause  their  oxidation,  or  it  may  cause 
them  to  break  up  into  several  oxidized  compounds  Through  the  agency 
of  its  moisture,  it  may  dissolve  some  of  these  secondary  substances  or 
it  may  form  with  them  hydrated  compounds  The  substances  thus 
formed  may  be  dissolved  in  water  and  carried  off,  or  they  may  remain 
to  mark  the  place  of  the  mineral  from  which  they  were  derived 

Water,  containing  traces  of  salts,  or  gases  in  solution  are  exceedingly 
active  agents  in  effecting  changes  in  minerals  Many  examples  of  the 
alteration  of  practically  insoluble  minerals  under  the  influence  of  dilute 
solutions  are  known  Calcite  (CaCOs),  for  instance,  when  acted  upon 
by  a  solution  of  magnesium  chloride  (MgCb)  takes  up  magnesium  and 
loses  some  ©f  its  calcium  Monticelhte  (CaMgSi04)  when  acted  upon 
by  solutions  of  alkaline  carbonates  breaks  up  into  a  magnesium  silicate 
and  calcium  carbonate.  Dilute  solutions  of  various  salts  are  constantly 
circulating  through  the  earth's  crust  and  are  there  effecting  trans- 
formations in  the  minerals  with  which  they  come  in  contact  On,  or 
near,  the  surface  the  transformations  are  taking  place  more  rapidly 
than  elsewhere  because  here  the  solutions  are  aided  in  their  decompos- 
ing action  by  the  gases  of  the  atmosphere 

The  effect  of  the  air  in  causing  alteration  is  seen  in  the  green  coat- 
ing of  malachite  ((CuOH^COs)  that  covers  surfaces  of  copper  or  of 
copper  compounds  exposed  to  its  action  In  this  particular  case  the 
coating  is  due  to  the  action  of  the  carbon  dioxide  and  the  moisture  of 
the  atmosphere.  Other  substances  in  contact  with  the  air  are  coated 
with  their  own  oxides,  sulphides,  etc. 

Pseudomorphs  —When  the  alteration  of  a  mineral  has  proceeded 
in  such  a  manner  that  the  new  products  formed  have  replaced  it  particle 
by  particle  a  pseudomorph  results  Sometimes  the  newly  formed  sub- 
stance crystallizes  as  a  single  homogeneous  gram  filling  the  entire 
space  occupied  by  the  original  substance  Usually,  however,  the  alter- 



ation  begins  along  the  surfaces  of  cracks  or  fissures  in  the  body  under- 
going alteration,  or  upon  its  exterior,  thus  producing  the  new  material 
at  several  places  contemporaneously  (Fig  10)  When  the  replace- 
ment takes  place  m  this  manner  the  resulting  mass  is  a  network  of 
fibers  of  the  new  substance  or  an  aggregate  of  grains  with  the  outward 
form  of  the  replaced  mineral 

With  respect  to  their  method  of  formation  chemical  pseudomorphs 
may    be    classified    as    alteration 
pseudomorphs     and    replacement 

Alteration  Pseudomorphs.  — 
Pseudomorphs  of  this  class  may 
be  defined  as  those  which  retain 
some  or  all  of  the  constituents  of 
the  original  minerals  from  which 
they  were  derived. 

Paramorphs.  —  Pseudomorphs 
composed  of  the  material  of  the 
pseudomorphed  substance  with- 
out addition  or  subtraction  of 
any  component  are  known  as 

Paramorphism  is  possible  only 
in  the  case  of  dimorphous  bodies. 
It  results  from  the  rearrangement 
into  new  bodies  of   the  particles  of  which  the  original  body  was  com- 

Illustrations  Calcite  (hexagonal  CaCOs)  after  aragomte  (ortho- 
rhombic  CaCOs),  orthorhombic  sulphur  after  the  monoclinic  variety. 

Partial  Pseudomorphs. — The  great  majority  of  pseudomorphs 
retain  a  portion,  but  not  all,  of  the  material  of  the  original  mineral 
They  may  be  formed  by  the  addition  of  material  to  the  original  body, 
by  the  loss  of  material  from  it,  or  by  the  replacement  of  a  portion  of 
its  material  by  new  material 

Pseudomorphs  formed  by  the  addition  of  substance  to  that  already 
existing  are  rare  The  substances  most  frequently  added  in  the  pro- 
duction of  such  pseudomorphs  are  oxygen,  sulphur,  the  hydroxyl 
group  (OH)  and  the  carbonic  acid  group  (CDs  and  COs) 

Illustrations  Malachite  ((CuOH^COs)  after  copper,  aoid  argentvte 
(Ag2S)  after  s^her. 

Pseudomorphs  resulting  from  the  loss  of  material  are  not  common. 

FIG  10  — Alteration  of  Ohvine  into  Ser- 
pentine The  alteration  is  proceeding 
from  the  surface  of  the  crystal  and 
from  surfaces  of  cracks  that  tra\erse 
it  The  black  specks  and  streaks 
represent  magnetite  formed  during  the 
process  (After  Tschermak ) 


They  are  caused  by  the  abstraction  of  one  or  more  of  the  constituents 
of  a  compound 

Illustration    Native  copper  after  cupnte  (Cu20) 

The  greater  number  of  partial  pseudomorphs  are  formed  by  the  sub- 
stitution of  some  of  the  components  of  the  original  mineral  by  a  new 

Illustrations  Limonite  (Fe403(OH)6)  pseudomorphs  after  sidente 
(FeCOs)  may  be  formed  by  the  following  reaction 

4FeC03+  20+3H20  =  4C02+Fe403(OH)  6 
Cerussite  (PbCOs)  may  be  formed  from  galena  (PbS),  thus 
PbS+40+Na2C03  =  PbC03+Na2S04 

Replacement  Pseudomorphs.  —  Often  the  entire  substance  of  a 
mineral  is  replaced  by  new  material,  so  that  no  trace  of  its  original 
matter  remains  In  this  case  the  nature  of  the  pseudomorphed  min- 
eral can  be  discovered  only  from  the  form  of  the  pseudomorph 

Illustrations  Quartz  (Si02)  after  calcite  (CaCOa)  and  gypsum 
(CaSO4  2H20)  after  halite  (NaCl) 

Mechanical  Pseudomorphs.  —  The  processes  described  above  as 
originating  pseudomorphs  are  chemical,  and  the  resulting  pseudomorphs 
are  sometimes  designated  chemical  pseudomorphs  There  is  another 
class  of  pseudomorphs,  however,  in  which  the  substance  of  a  crystal 
has  not  been  replaced  gradually  by  the  pseudomorphing  substance 
In  this  class  the  pseudomorphing  substance  simply  fills  a  mold  left  by 
the  solution  of  some  preexisting  crystal  Thus,  if  a  sulphur  crystal 
should  become  encrusted  with  a  coating  of  bante  (BaS04)  and  the 
temperature  should  rise  until  the  sulphur  melts  and  escapes,  there 
would  be  left  a  mold  of  itself  constructed  of  bante  If,  now,  a  solution 
of  calcium  carbonate  should  penetrate  the  cavity  and  fill  it  with  a  deposit 
of  calcite  (CaCOs),  the  mass  of  calcite  would  have  the  shape  of  a  crystal 
of  sulphur.  Pseudomorphs  of  this  kind  are  known  as  mechanical 

Weathering.—The  term  weathering  is  applied  to  the  sum  of  all  the 
changes  produced  in  minerals  by  the  action  of  the  atmosphere  upon 
them  Although  nearly  all  minerals  show  some  traces  of  weathering, 
these  traces  may  often  be  detected  only  by  the  slight  differences  m  color 
exhibited  by  surfaces  that  have  been  exposed  for  a  long  time  to  the 
action  of  the  air  when  compared  with  fresh  surfaces  produced  by  frac- 
ture or  cleavage, 


The  weathering  of  minerals  is  often  of  great  economic  importance 
Veins  of  sulphides  and  a  few  other  compounds  may  be  oxidized  where 
they  outcrop  on  the  surface  Some  of  the  decomposition  products  thu? 
formed  may  be  soluble  and  others  insoluble  The  insoluble  products 
may  remain  near  the  surface  while  the  soluble  ones  are  carried  down- 
ward by  ground  water  along  the  course  of  the  vein  Here  a  reaction 
may  ensue  between  the  soluble  salts  and  the  undecomposed  portion  of 
the  vein  with  the  result  that  metallic  compounds  may  be  precipitated, 
thus  enriching  the  original  vein  matter  and  causing  it  to  be  changed 
from  a  comparatively  lean  ore  to  one  of  great  richness 

Pynte  veins  on  the  surface  are  often  marked  by  accumulations  of 
hmonite  derived  by  the  oxidation  of  the  sulphide  With  this  may  be 
mixed  insoluble  carbonates,  silicates  and  other  salts  of  valuable  metals 
present  in  the  original  sulphide  Weathering  may  extend  downward 
along  the  veins  for  a  short  distance,  replacing  their  upper  portions  with 
the  oxidized  decomposition  products  This  portion  of  a  vein  is  often 
spoken  of  as  the  o  wdized  zone,  and  this  is  sometimes  the  richest  portion 
of  the  vein  It  may  be  rich  because  less  valuable  substances  have 
formed  soluble  salts  and  have  been  drained  away 

Below  the  oxidized  zone  may  be  another  zone  less  rich  in  valuable 
compounds  than  the  oxidized  zone,  but  much  richer  than  the  material 
below  it  The  soluble  decomposition  products  of  the  upper  portion  of 
the  vein  may  percolate  downward,  and  react  with  the  unchanged  vein 
matter,  precipitating  valuable  metallic  salts  Although  the  original 
vein  matter  may  contain  an  inconsiderable  quantity  of  the  valuable 
material,  the  precipitation  in  it  of  additional  stores  of  material  of  the 
same  kind  may  raise  the  percentage  of  this  constituent  to  a  point  where 
it  is  profitable  to  mine  it  This  belt  of  enriched  ore  is  known  as  the 
zone  of  secondary  em  ichment 

The  oxidized  zone  extends  downward  from  the  surface  to  a  depth  at 
which  the  atmosphere  and  meteoric  water  become  exhausted  of  their 
oxygen — a  depth  which  varies  with  local  conditions  The  zone  of 
secondary  enrichment  extends  from  the  bottom  of  the  oxidized  zone 
to  a  short  distance  below  the  level  of  the  ground  water,  beyond  which 
solutions  will  diffuse  and  thus  be  carried  away  from  the  vein.  Below 
the  zone  of  enrichment  the  original  vein-filling  may  reach  downward 
indefinite  distances 

Since  many  veins  exhibit  the  features  described,  it  follows  that  the 
ore  of  many  mines  must  grow  poorer  with  depth,  and  that  in  many 
instances  the  richest  ore  is  near  the  surface 

Some  of  the  changes  involved  in  weathering  and  secondary  enrich- 


ment  of  sulphide  veins  in  limestone  are  indicated  by  the  following  reac- 
tions in  the  case  of  a  vein  containing  pyrite  (FeS2),  sphalerite  (ZnS), 
and  galena  (PbS) 

(1)  The  first  change  produced  at  the  surface  may  be  the  oxidation 
of  the  sulphides  to  sulphates 

(a)  ZnS+40=ZnS04, 

(b)  PbS+40=PbS04  (anglesite); 

(c)  FeS2+70+H20=H2S04+FeS04 

(2)  These  may  react  with  the  limestone  as  follows 

(smithsomte)          (gypsum) 

(a)  ZnS04+CaC03+2H20=ZnC03    +    CaS04  2H20, 

(cerussite)  (gypsum) 

(b)  PbS04+CaCO3+2H20=PbC03    +    CaS04 

(3)  Some  of  the  sulphates  and  carbonates  carried  down  into  the  un- 
altered sulphides  may  react  with  these,  yielding 

(a)  PbS04+FeS2+02=PbS+FeS04+S02, 

(galena)      (sidente) 
(J)  PbC03+FeS2+02=PbS    +    FeCOs    +    S02; 

GO  PbS04+ZnS  =  PbS+ZnS04, 

(galena)     (smithsonite) 
(<0  PbC03+ZnS  =  PbS    +    ZnC03 

The  PbS  replacing  the  ZnS  and  deposited  in  the  cracks  in  the  original 
mixture  of  PbS,  ZnS  and  FeS2  increases  the  percentage  of  this  compound 
in  the  vein  and  thus  enriches  it. 

There  is  also  an  increase  in  the  percentage  of  ZnS  brought  about  by 
the  reactions  between  the  zinc  salts  (ia  and  20),  and  the  pyrite,  analogous 
to  those  between  the  lead  salts  and  pyrite  (30  and  36)  Thus 

ZnS04+FeS2+02    =    ZnS    +    FeS04+S02, 

ZnC03+FeS2+02    =    ZnS    +    FeC03+S02. 


The  zinc  salts  produced  in  reactions  $c  and  $d  if  carried  downward  will 
also  have  the  opportunity  to  react  \\ith  the  pynte  in  the  same  way 

If  the  ZnS  is  deposited  in  fissures  in  the  vein  matter  this  will  tend  to 
enrich  it  with  zinc 

The  oxidized  zone  contains  (smithsonite)  ZnCOs,  (anglesite)  PbSO4, 
(cerussite)  PbCOa  and  (limomte)  Fe2(OH)2  The  ZnS04,  formed  also 
in  the  oxidized  zone,  is  so  readily  soluble  in  water  that  it  is  leached  from 
the  other  oxidized  compounds  and  is  carried  downward. 




OF  the  1,000  or  more  distinct  minerals  recognized  by  mineralogists 
only  a  few  (some  250)  are  common  A  few  are  important  because  they 
constitute  ores,  others  because  they  are  components  of  rock  masses, 
and  others  simply  because  of  their  great  abundance  Only  a  few  miner- 
alogists profess  acquaintance  with  more  than  500  or  600  minerals  The 
majority  are  familiar  with  but  300  or  400,  relying  for  the  identification  of 
the  remainder  upon  the  descriptions  of  them  recorded  in  mmeralogical 

Only  the  minerals  commonly  met  with  and  those  of  economic  or  of 
special  scientific  importance  are  described  m  this  book  They  should 
be  studied  with  specimens  before  one,  in  order  that  the  relation  between 
the  descriptions  and  the  objects  studied  may  be  forcibly  realized  Min- 
eralogy cannot  be  studied  successfully  from  books  alone  It  is  primarily 
a  study  of  objects  and  consequently  the  objects  should  be  at  hand  for 
inspection l 

Mineral  Names. — The  names  of  the  great  majority  of  minerals  end 
in  the  termination  "ite  "  This  is  derived  from  the  ancient  Greek  suffix 
"itis"  which  was  always  appended  to  the  names  of  rocks  to  signify  that 
they  are  rocks  The  first  portion  of  the  name,  to  which  the  suffix  is 
added,  either  describes  some  quality  or  constituent  possessed  by  the 
mineral,  refers  to  some  common  use  to  which  it  has  been  put,  indicates 
the  locality  from  which  it  was  first  obtained,  or  is  the  name  of  some 
person  intended  to  be  complimented  by  the  mineralogist  who  first 
described  the  mineral  bearing  it 

1  Collections  of  the  common  minerals  in  specimens  large  enough  for  convenient 
study  may  be  secured  at  small  cost  from  any  one  of  the  mineral  dealers  whose 
addresses  may  be  found  m  any  mmeralogical  journal 


The  following  examples  taken  from  Dana  illustrate  some  of  these 
principles  The  mineral  hematite  (Fe203)  is  so  named  because  of  the  red 
color  of  its  powder,  chlorite  (a  complicated  silicate),  because  of  its  green 
color,  sidente  (FeCOs),  from  the  Greek  word  for  iron,  because  it  con- 
tains this  metal,  magnetite  (FeaO-i)  after  Magnesia  in  Asia,  goethite 
(FeO(OH))  after  the  poet  Goethe 

The  names  of  a  few  minerals  end  in  "ine,"  "ane,"  ^ase,"  ^ote,"  etc , 
but  the  present  tendency  is  to  ha\  e  them  all  end  in  "ite  "  Occasionally, 
the  same  mineral  may  have  two  names  This  may  be  due  to  the  fact 
that  it  was  discovered  by  two  mineralogists  working  at  the  same  tune 
in  different  places,  or  it  may  be  due  to  the  fact  that  the  mineralogists  of 
different  countries  prefer  to  follow  different  precedents  set  by  the  old 
mineralogists  of  their  respective  nationalities  For  example,  the  min- 
eral (Mg  Fe)sSi04  is  called  ohmne  by  the  Germans  and  by  most  English- 
speaking  mineralogists,  and  peridot  by  the  French  The  Germans  follow 
the  German  mineralogist  Werner,  who  first  used  the  name  ohvine  in 
1789,  while  the  French  follow  the  French  teacher  Hauy,  who  proposed 
the  name  peridot  in  1801 


The  elements  that  occur  in  nature  are  few  in  number,  and  these, 
with  rare  exceptions,  do  not  occur  in  great  abundance  They  may  be 
separated  into  the  following  groups  the  carbon  group,  the  sulphur 
group,  the  arsenic  group,  the  silver  group,  and  the  platinum-iron 
group  Some  of  these  comprise  only  a  single  mineral,  while  others 
comprise  six  or  seven  Only  a  portion  of  these  are  described 



The  carbon  group  embraces  several  minerals  of  which  one  is  dia- 
mond, another  is  an  amorphous  black  substance  known  as  schungite, 
and  the  other  two  are  apparently  but  different  forms  of  graphite 
The  element  may  thereupon  be  regarded  as  tnmorphous  Diamond 
and  graphite  are  both  important. 

Isometric  (hextetrahedral)  Hexagonal  (ditngonal  scalenohedral) 

Diamond  Graphite 

Diamond  (C) 

The  diamond  is  usually  found  in  distinct  crystals  or  in  irregular 
masses,  varying  m  size  from  a  pin's  head  to  a  robin's  egg  In  some 
cases  large  individual  pieces  are  found  but  they  "-are  exceedingly  rare 



FIG  ii  — Etch  Figures  on 
Cubic  Face  of  Diamond 
Crystal  (After  Tscher- 

The  largest  ever  found,  known  as  the  Cullman  diamond  (Fig  16), 
weighed  3,024!  carats  or  621  grams,  or  i  37  Ib  , 
and  measured  112x64x51  mm  It  was  cut 
into  nine  fine  gems  and  a  number  of  smaller 
ones  (Fig  17) 

In  composition  the  diamond  is  pure  car- 
bon, but  it  is  a  form  of  carbon  that  is  not 
ignited  and  burned  at  low  temperatures  At 
high  temperatures,  however,  especially  when 
in  the  presence  of  oxygen,  it  burns  freely 
with  the  production  of  CC>2,  and,  in  the  case 
of  opaque  varieties,  a  little  ash 

Its  crystallization  is  isometric  (hextetra- 
hedral  class),  and  the  forms  on  the  crystals  often  appear  to  be  tetra- 
hedrally  hemihedral,  although  the 
etch  figures  on  cubic  faces  suggest 
hexoctahedral  symmetry  (Fig  n). 
Octahedrons,  tetrahedrons,  icositet- 
rahedrons  and  combinations  of  these 
forms  are  common,  and  in  nearly  all 
cases  the  interf acial  edges  are  rounded 
and  the  crystal  faces  curved  Some- 
times this  curving  is  so  pronounced 
that  the  individuals  are  practically 
spheres  (Fig  12)  Twins  are  com- 
mon with  0(in)  as  the  twinning 
plane  (Fig  13), 

The  cleavage  of  diamond  is  per- 
fect parallel  to  the  octahedral  face. 
This  is  an  important  characteristic,  as  the  lapidary  makes  use  of  it 
in  the  preparation  of  stones  for  cutting  Its 
fracture  is  conchoidal  Its  specific  gravity  is 
3  52  and  its  hardness  greater  than  that  of  any 
other  known  substance  Most  diamonds  are 
dark  and  opaque,  or,  at  most,  translucent,  but 
many  are  found  that  are  transparent  and  color- 
less or  nearly  so  Gray,  brown,  green,  yellow, 
blue  and  red  tinted  stones  are  also  known,  and, 
with  the  exception  of  the  blue  and  red  diamonds, 
these  are  more  common  than  the  colorless,  or 
luster  of  all  diamonds  is  adamantine,  and 

FIG    12 — Crystal  of  Diamond  with 
Rounded  Edges  and  Faces     (Krantz ) 

FIG  13 — Octahedron  of 
Diamond  Twinned 

so-called  white  stones 


their  index  of  refraction  is  very  high,  n=z  4024  for  red  rays,  2  4175  for 
yellow  rays,  and  2  4513  for  blue  ra>s  In  consequence  of  their  strong 
dispersion,  the  reflection  of  light  from  the  inner  surfaces  of  transparent 
stones  is  very  noticeable,  causing  them  to  sparkle  brilliantly,  with  a 
handsome  play  of  colors  It  is  this  latter  fact  and  the  great  hardness 
of  the  mineral  that  make  it  the  most  valuable  of  the  gems  The  mineral 
is  a  nonconductor  of  electricity 

Three  varieties  of  the  diamond  have  received  distinct  names  in 
the  trade  These  are 

Gem  diamonds,  which  are  the  transparent  stones, 

Bort,  or  Bortz,  gray  or  black  translucent  or  opaque  rounded  masses, 
with  a  rough  exterior  and  the  structure  of  a  crystalline  aggregate,  and 

Carbonado,  black,  opaque  or  nearly  opaque  masses  possessing  a 
crystalline  structure,  but  no  distinct  cleavage 

The  only  minerals  with  which  diamond  is  liable  to  be  confused 
are  much  softer,  and,  consequently,  there  is  little  difficulty  in  dis- 
tinguishing between  them 

Syntheses  — Small  diamonds  have  been  made  by  fusing  in  an 
electric  furnace  metallic  iron  containing  a  small  quantity  of  carbon  and 
cooling  the  mass  suddenly  in  a  bath  of  molten  lead  They  have  also 
been  made  by  heating  in  the  electric  arc  pulverized  carbon  on  a  spiral 
of  iron  wire  immersed  m  hydrogen  under  a  pressure  of  3,100  atmospheres 
A  third  method,  which  resulted  in  the  production  of  tiny  octahedrons, 
consisted  in  melting  graphite  in  olivine,  or  in  a  mixture  of  silicates 
having  the  composition  of  the  South  African  "  blue  ground,"  with 
the  addition  of  a  little  metallic  aluminium  or  magnesium 

Occurrence  and  Origin — Diamonds  are  found  (i)  in  clay,  sand 
or  gravel  deposits  or  in  the  rocks  formed  by  the  consolidation  of  these 
substances,  where  they  are  associated  with  gold,  platinum,  topaz, 
garnet,  tourmaline  and  with  other  minerals  that  result  from  the  decom- 
position of  granitic  rocks,  (2)  in  a  basic  igneous  rock  containing  frag- 
ments of  shale  (a  consolidated  mud)  and  (3)  small  diamonds  have  been 
discovered  in  meteorites 

The  manner  of  origin  of  diamonds  has  been  a  subject  of  contro- 
versy for  many  years  The  most  popular  theory  ascribes  the  diamonds 
in  igneous  rocks  to  the  solution  of  organic  matter  m  the  rock  magmas 
and  the  crystallization  of  the  carbon  upon  cooling  Another  theory 
regards  the  carbon  as  an  original  constituent  of  the  magma.  The 
diamonds  in  sand,  sandstone,  granite,  etc ,  are  believed  to  have  been 
transported  from  their  original  sources  and  deposited  in  river  channels 
or  on  beaches. 


Localities  — The  principal  localities  from  which  diamonds  are  obtained 
are  the  Madras  Presidency  in  India,  the  Province  of  Mmas-Geraes  in 
Brazil,  the  Island  of  Borneo,  the  valleys  of  the  Vaal  and  Orange 
Rivers,  and  other  places  in  South  Africa,  and  the  valley  of  the  Mazarum 
River  and  its  tributaries  in  British  Guiana  Recently  diamond  fields 
have  been  discovered  in  New  South  Wales,  Australia,  in  the  \alley  of 
the  Kasai  River  m  the  Belgian  Kongo,  in  Arkansas,  and  in  the  Tula- 
meen  district,  British  Columbia 

In  the  United  States  a  few  gem  diamonds  have  been  found  from 
tune  to  time  in  Franklin  and  Rutherford  counties  in  North  Carolina, 
in  the  gold-bearing  gravels  of  California,  and  m  soils  and  sands  in  the 
states  of  Alabama,  Virginia,  Wisconsin,  Indiana,  Ohio,  Idaho  an^l 
Oregon  A  stone  (the  Dewey  diamond)  found  near  Richmond,  Virginia, 
a  few  years  ago  is  valued  at  $300  or  $400 

The  principal  source  of  diamonds  and  carbonado  in  Brazil  at  the 
present  time  is  Bahia,  where  the  mineral  occurs  in  a  friable  sandstone 
along  river  courses  The  output  of  this  region  has  decreased  so  greatly 
in  the  last  few  years  that  although  a  mass  of  carbonado  weighing  3,073 
carats  (the  largest  mass  of  diamond  material  ever  found)  was  obtained 
in  1895,  the  price  of  this  impure  diamond  rose  from  $10  50  per  carat 
m  1894  to  $36  oo  per  carat  in  1896  and  $85  oo  per  carat  for  the  best 
quality  m  1916 

The  only  diamond  field  of  prominence  m  the  United  States  is  that 
which  has  recently  been  exploited  near  Murfreesboro  in  Arkansas,  where 
the  conditions  are  similar  to  those  existing  in  South  Africa  The  dia- 
monds occur  m  a  basic  igneous  rock  (pendotite)  that  cuts  through  Scind- 
stones  and  quartzites  The  pendotite  is  weathered  to  a,  soft  earth  or 
"  ground  "  m  which  the  diamonds  are  embedded  Up  to  the  end  of 
1914  over  2,000  diamonds  had  been  found,  mostly  small  stones  weighing 
in  the  aggregate  550  carats,  valued  at  about  $12,000  One,  however, 
weighed  8§  carats  and  another  7^  carats  The  rough  unsorted  stones 
are  valued  at  $10  per  carat  Three  stones  that  were  cut  were  found 
to  be  worth  from  $60  to  $175  per  carat  The  district  has  not  yet  been 
sufficiently  developed  to  prove  its  commercial  value  The  diamonds 
in  British  Columbia  occur  in  the  same  kind  of  rock  as  those  m  Arkansas 
The  few  that  have  thus  far  been  found  are  too  small  for  any  practical 

In  former  times  the  mines  of  India  and  Borneo  were  very  produc- 
tive, the  famous  Golconda  district  m  India  for  a  long  period  furnishing 
most  of  the  gems  to  commerce 

The  African  mines  were  opened  in  1867     Since  this  time  they 

— mil,  Ji/JjJkMIiJWTS  41 

have  been  practically  the  only  producers  of  gem  material  in  the  world 
It  is  estimated  that  the  quantity  of  uncut  diamonds  yielded  by  the 
mines  near  Kimberly  alone  have  amounted  in  value  to  the  enormous 
sum  of  $900,000,000  The  output  of  the  African  mines  in  1913  was 
sold  for  about  $53,000,000,  being  over  95  per  cent  of  the  world's  out- 
put of  gem  material  Of  this  amount  about  $9,000,000  worth  of  stones 
were  furnished  by  German  Southwest  Africa,  the  balance  by  the 
Union  of  South  Africa  The  diamonds  are  found  in  a  pendotite  which 
occurs  in  the  form  of  volcanic  necks,  or  "  pipes,"  cutting  carbonaceous 
shales  The  igneous  rock  is  much  weathered  to  a  soft  blue  earthy  mass 
known  as  "  blue  earth  "  Near  the  surface  where  exposed  to  the  action 
of  the  atmosphere  the  earth  is  yellow  The  diamonds  are  scattered 
through  the  weathered  material  in  quantities  amounting  to  between 
3  and  6  carat  per  cubic  yard 

E\tr action  — Where  the  diamond  occurs  in  sand  and  gravel  it  is  ob- 
tained by  washing  away  the  lighter  substances 

In  South  Africa  and  Arkansas  the  mineral  is  found  in  a  basic  volcanic 
rock  which  weathers  rapidly  on  exposure  to  the  air  The  weathered 
rock  is  mined  and  spread  on  a  prepared  ground  to  weather  When  suf- 
ficiently disintegrated  water  is  added  to  the  mass  and  the  mud  thus 
formed  is  allowed  to  pass  over  plates  smeared  with  grease  The  dia- 
monds and  some  of  the  other  materials  adhere  to  the  grease,  but  most 
of  the  valueless  material  is  carried  off  by  the  water 

Uses — Transparent  diamonds  constitute  the  most  valuable  gems 
in  use  Perfectly  white  stones,  or  those  possessing  decided  tints  of  red, 
rose,  green  or  blue  are  the  most  highly  prized  They  are  sold  by 
weight,  the  standard  being  known  as  the  carat,  which,  until  recently, 
was  equivalent  to  3  168  grains  or  205  milligrams  At  present  the  metric 
carat  is  m  almost  universal  use  This  has  a  weight  of  200  milligrams 
The  price  of  small  stones  depends  upon  their  color,  brilliancy  and  size — 
a  perfectly  white,  brilliant,  cut  stone  weighing  one  carat,  being  valued 
at  about  $175  oo  As  the  size  increases  the  value  increases  in  a  much 
greater  ratio,  the  price  obtained  for  large  stones  depending  almost  solely 
upon  the  caprice  of  the  purchaser 

Nearly  all  the  gem  diamonds  put  upon  the  market  are  cut  before 
being  offered  for  sale  The  chief  centers  of  diamond  cutting  are  Ant- 
werp and  Amsterdam  in  the  Old  World  and  New  York  in  America 
The  favorite  cuts  are  the  brilliant  and  the  rose  For  the  former  only 
octahedral  crystals,  or  those  that  will  yield  octahedrons  by  cleavage, 
are  used,  for  the  rose  cut  distorted  octahedrons  or  twinned  crystals 
In  producing  the  "brilliant"  a  portion  of  the  top  of  an  octahedron  is  cut 



off  and  a  small  portion  of  the  bottom     On  the  remainder  are  cut  three 
or  four  bands  of  facets  running  horizontally  around  the  stone  (see  Fig  14) 
The  "rose"  has  a  flat  base  surmounted  by  a  pyramidal  dome  consisting 
of  24  or  more  facets     In  late  years  the  shapes  into  which  diamonds  are 
cut  have  been  determined  less  by  the  decrees  of  fashion  and  more  by  the 

desire  to  sa\e  as  much  ma- 
terial as  possible,  and,  conse- 
quently, irregularly  shaped  cut 
diamonds  are  much  more 
common  than  formerly  (com- 
pare Fig  17). 

Diamonds  are  employed 
also  as  cutting  tools  Small 
fragments,  or  splinters  of  gem 
quality,  are  used  for  cutting 
and  polishing  diamonds  and 


Grona  Back,  or  Pavilion 

Step   or  Trap 


Side  View 

Pavilion,  or  Base 

FIG  14  — Principal  "  cuts  "  of  Diamonds 

other  gems,  and  small  crystals 
with  crystal  edges  for  cutting 
glass  Small  cleavage  pieces 
are  utilized  in  the  manufacture  of  engravers'  tools  and  writing  instru- 
ments Recently  diamonds  with  small  holes  of  from  008  to  0006  of  an 
inch  drilled  in  them,  have  been  employed  as  wne  dies 

Bort  is  also  used  as  a  polishing  and  cutting  material,  while  carbonado, 
nearly  all  of  which  comes  from  Brazil,  is  used  in  the  manufacture  of 
boring  instruments  Diamond  drills  consist  of  hollow  cylinders  of  soft 
iron  set  at  their  lower  edges  with  6,  8  or  12  black  diamonds  By  rapid 
revolution  of  this  a  "core"  may  be  cut  from  the  hardest  rocks 

Some  Famous  Diamonds  — The  largest  diamond  ever  found — the  Cull- 
inan— was  picked  up  at  the  Premier  Mine  (Fig  15)  in  the  Transvaal  in 
January,  1905,  and  was  presented  to  King  Edward  of  England  as  a  birth- 
day gift  in  1908  (Figs  16  and  17  )  It  weighed  about  3,025  carats  (about 
i  37  pounds)  The  next  largest  was  found  in  June,  1893,  at  the  Jagers- 
fontem  mine  It  is  known  as  the  Excelsior  It  weighed  in  its  natural 
state  971  carats  and  was  3  inches  long  in  its  greatest  dimension  It  was 
valued  at  $2,000,000  It  is  said  to  have  been  presented  by  the  Presi- 
dent of  The  Orange  Free  State  to  Pope  Leo  XIII  The  third  largest 
stone  is  the  Reitz  It  is  a  640-carat  stone  found  at  the  same  mine  during 
the  close  of  1895  This,  though  smaller,  is  said  to  be  handsomer  than  the 
Excelsior  The  most  noted  diamond  in  the  world  is  the  Kohmoor,  which 
weighed,  before  cutting,  186  carats  It  is  now  a  brilliant  of  106  carats, 
belonging  to  the  crown  of  England  Other  famous  diamonds  aie  the 



FIG  15, — Premier  Diamond  Mines  in  South  Africa 

pIG  X6,— -The  Cullman  Diamond.    (Natural  size ) 


FIG  17  — Gems  Cut  from  the  Cullman  Diamond      (Two-lifthb  nat  si/c  ) 

Orlov,  193  carats,  the  property  of  Russia,  the  Regent  or  Pitt  diamond 
of  137  carats  belonging  to  France,    the  Green  diamond  of  Dresden, 

weighing  48  carats,  and  the  Blue 
Hope  diamond,  weighing  44  carats 
The  "  Star  of  the  South,"  found  in 
Brazil,  weighed  254  carats  bcfoie 
cutting  and  125  .iftcnvard  The 
Victoria  diamond  from  one  of  the 
Kimberly  mines  -weighed  457  carats 
\\hen  found  It  has  been  cut  to  a 
perfect  brilliant  of  180  carats  valued 
at  $1,000,000  The  Tiffany  dia- 
mond (Fig  1 8)  now  owned  in  New 
York  is  a  double  brilliant  of  a 
golden  yellow  color  weighing  128^ 
carats  (25  702  grams)  and  valued  at 
$100,000  When  it  is  remembered 
that  a  five-carat  stone  is  large,  the 
enormous  proportions  of  the  above-named  gems  are  better  appreciated. 

FIG  1 8 —-The  Tiffany  Diamond    (Nat- 
ural size )     (Kindness  of  TiJJany  &•  Co ) 

Graphite  (C) 

Graphite,  or  plumbago,  occurs  principally  in  amorphous  masses  of  a 
black,  clayey  appearance,  in  radiated  masses,  in  brilliant  lead  black 
scales  or  plates,  and  occasionally  in  crystals  with  a  rhombohedral  habit 

Like  diamond,  graphite  consists  of  carbon  Crystals  from  Ceylon 
yield  C=794o,  Ash=is  50,  Volatile  matter=s  10.  The  mineral  is 
often  impure  from  admixture  with  clay,  etc. 


Crystals  of  the  material  ar«e  so  rare  that  their  symmetry  is  still  in 
doubt  Their  habit  is  hexagonal  (ditngonal  scalenohedral  class) 
Measurements  made  on  the  interfacial  angles  of  crystals  from  Ticon- 
deroga,  New  York,  gave  a  c=i  i  3859  These  possess  a  rhombo- 
hedral  symmetry  All  crystals  are  tabular  and  nearly  all  are  so  distorted 
that  the  measurements  of  their  interfacial  angles  cannot  be  depended 
upon  for  accuracy  They  apparently  contain  the  planes  R(ioTi), 

OP(IOOO),    COP2(II20),  and  2P2(lI2l) 

Graphite  is  black  and  earth} ,  or  lustrous,  according  as  it  is  impure 
or  pure  It  is  easily  clea\  able  parallel  to  the  basal  plane  and  the  cleav- 
age laminae  are  flexible  It  is  very  soft,  its  hardness  being  only  1-2, 
its  density  about  2  25  Its  luster  is  metallic  and  the  mineral  is  opaque 
even  in  the  thinnest  flakes  It  is  a  conductor  of  electricity 

Graphite  is  infusible  and  noncombustible  even  at  moderately  high 
temperatures  Like  diamond,  however,  it  may  be  burned  under  cer- 
tain conditions  at  \  ery  high  temperatures  (65o°-7oo°)  It  is  unaffected 
by  the  common  acids  and  is  not  acted  upon  by  the  atmosphere 
When,  ho\\e\er,  it  is  subjected  to  the  action  of  strong  oxidizing  agents, 
such  as  a  \\arm  mixture  of  potassium  chlorate  (KClOj)  and  fuming 
nitric  acid,  it  changes  to  a  }ello\\  substance  kno^n  as  graphitic  acid 
(CnKLiOj)  It  is  thus  distinguished  from  amorphous  carbon,  like 
schungite  and  anthracite  Moreo\er,  man\  forms  of  graphite,  \\hen 
moistened  with  fuming  nitric  acid  and  heated,  s\\ell  up  and  send  out 
worm-like  processes  Those  \\hich  do  not  act  thus  are  called  graphititc 
Natural  graphite  is  of  both  types 

Its  color,  softness  and  infusibility  serve  to  distinguish  graphite  from 
all  other  minerals  but  molybdenite  (p  75)  It  ma\  be  distinguished  from 
this  mineral  by  the  fact  that  it  contains  no  sulphur 

Syntheses  — Crystalline  graphite  is  made  on  a  commercial  scale 
by  treating  anthracite  coal  or  coke  containing  about  5  75  per  cent  of 
ash  in  an  electric  furnace  It  also  separates  \\hen  molten  iron  con- 
taining dissolved  carbon  is  cooled 

Occurrence  and  Origin  — Graphite  occurs  as  thin  plates  and  scales 
m  certain  igneous  rocks,  m  gneisses,  schists  and  limestones,  as  large 
scales  m  coarse  granite  dikes  (pegmatite)  and  m  crystalline  limestones, 
and  as  amorphous  masses  at  the  contacts  of  igneous  rocks  with  carbona- 
ceous rocks  The  mineral  is  also  found  in  veins  cutting  sedimentary 
and  metamorphic  rocks  Crystals  are  found  only  in  limestone 

The  occurrence  of  graphite  m  sedimentary  and  igneous  rocks  sug- 
gests that  it  may  have  been  formed  m  several  ways  It  is  thought 
that  the  material  in  limestone  and  quartz-schist  may  represent  carbo- 


naceous  material  that  was  deposited  with  the  sediments  and  which  has 
since  been  carbonized  by  heat  and  pressure  The  material  m  peg- 
matite may  be  an  original  constituent  of  the  magma  that  produced  the 
rock,  and  the  graphite  may  be  the  product  of  pneumatolytic  processes , 
i  c ,  it  may  have  been  produced  by  deposits  from  vapors  that  accom- 
panied the  formation  of  the  pegmatite  If  this  be  true,  the  mineral 
found  in  metamorphosed  limestone  and  schist  may  be  of  contact  origin, 
i  e  ,  it  may  have  been  produced  by  the  migration  of  gases  and  solutions 
from  igneous  rocks  into  the  mass  of  the  surrounding  sediments  The 
vein  deoosits  probably  had  a  similar  origin,  the  mineral  having  been 
deposited  mainly  in  cracks  traversing  metamorphic  rocks  On  the 
other  hand,  graphite,  in  some  instances,  appears  to  be  a  direct  separa- 
tion from  a  molten  magma 

Localities  — The  principal  foreign  source  of  supply  for  commercial 
graphite  is  the  Island  of  Ceylon  In  the  United  States  the  mineral  has 
been  mined  on  the  southeast  side  of  the  Adirondacks  in  New  York, 
in  Chester  County,  Pennsylvania,  near  Dillon,  Montana,  at  several 
points  in  Arkansas,  Georgia,  Alabama  and  North  Carolina,  in  Wyo- 
ming, in  Baraga  County,  Michigan,  and  to  a  small  extent  in  Colorado, 
Nevada,  and  Wisconsin  It  occurs  also  abundantly  at  many  other 
places  Its  chief  source  in  the  United  States  is  Graphite,  near  Lake 
George,  New  York 

Preparation  — Graphite  is  obtained  on  a  commercial  scale  by  grind- 
ing the  rock  containing  it  and  floating  the  graphite  flakes 

Uses  —Crude  graphite,  or  plumbago,  is  used  in  the  manufacture  of 
stove  and  other  polishes,  and  of  black  paint  foi  metal  surfaces,  for  both 
of  which  it  is  especially  valuable  on  account  of  its  noncorrodmg  propji- 
ties  The  purified  mineral  is  mixed  with  clay  and  made  into  crucibles 
for  use  at  high  temperatures  It  is  also  ground  and  used  m  this  form 
as  a  lubricant  for  heavy  machinery,  and  is  compressed  into  u  black  lead  " 
centers  for  lead  pencils 

Production  —The  quantity  of  crude  graphite  mined  m  the  United 
States  during  1912  amounted  to  2,445  tons>  valued  at  $207,033,  besides 
which  there  were  manufactured  6,448  tons,  valued  at  $830,193.  The 
imports  were  25,643  tons,  valued  at  $709,337 

Schungjte  is  a  black,  amorphous  carbon  with  a  hardness  of  3-4 
and  a  spgr.  of  i  981  It  is  soluble  in  a  mixture  of  HNOs  and  KClOj 
without  the  production  of  graphitic  acid.  It  occurs  in  some  crystalline 




Sulphur  is  known  in  at  least  six  different  forms,  four  of  which  are 
crystalline  The  two  best  known  forms  crystallize  respectively  in  the 
orthorhombic  (orthorhombic  bipyramidal  class)  and  the  monoclimc 
(prismatic  class)  systems  The  former  separates  from  solutions  of  sulphur 
in  carbon  bisulphide  and  the  latter  separates  from  molten  masses 
Both  the  orthorhombic  and  the  monoclimc  phases  are  believed  to  be 
formed  by  natural  processes,  but  the  latter  passes  over  into  the  former 
upon  standing,  so  that  its  existence  as  a  mineral  cannot  be  definitely 
proven  Selenium  and  tellurium,  which  are  also  members  of  the  sul- 
phur group,  are  extremely  rare  Tellurium  occurs  in  rhombohedral 
crystals  and  selenium  in  mixed  crystals  of  doubtful  character  with 
sulphur  and  tellurium 

Sulphur  (S) 

Sulphur  occurs  in  nature  as  a  lemon-colored  powder,  as  spherical  or 
globular  masses,  as  stalactites  and  in  crystals 

Chemically  it  is  pure  sulphur,  or  a  mixture  of  sulphur  and  clay, 

FIG  19  FIG  20 

FIG    19— Sulphur  Crystals  with  P,  in  (£),  3?,  113  (s),  P»°,  on  («),  and  oP, 

ooi  (c) 

FIG  20  —Distorted  Crystal  of  Sulphur  (Forms  same  as  in  Fig.  19 ) 

bitumen  or  other  impurities.  It  sometimes  contains  traces  of  tellu- 
rium, selenium  and  arsenic 

Crystals  of  sulphur  are  usually  well  formed  combinations  of  ortho- 
rhombic  bipyramids  and  domes,  with  or  without  basal  terminations. 
Their  axial  ratio  =  8108  *  i  i  9005  The  principal  forms  observed 
are  P(in),  POO(IOI),  P  £6(011),  iP(ii3)  and  oP(ooi)  (Figs  19  and 
20)  The  habit  of  the  crystals  is  usually  pyramidal,  though  crystals 
with  a  tabular  habit  are  quite  common 

Crystals  of  sulphur  are  yellow     Their  streak  is  light  lemon  yellow, 


The  mineral  has  a  resinous  luster  Its  hardnebs  is  only  i  5-2,  and 
density  about  204  Its  fracture  is  conchoidal  and  cleavage  imper- 
fect It  is  transparent  or  translucent,  is  brittle  and  is  a  non- 
conductor of  electricity  Its  indices  of  refraction  for  sodium  light 
area  =  i  9579,  j8«a  0377,  7  =  2  2452 

Massive  sulphur  varies  in  color  from  yellow  to  yellowish  brown 
greenish  gray,  etc  ,  according  to  the  character  and  amount  of  impurities 
it  contains  Its  powder  is  nearly  always  crystalline  In  mass  it  pos- 
sesses a  lighter  color  than  the  crystals  or  the  massive  sulphur 

At  a  temperature  of  114°  sulphur  melts,  and  at  270°  it  ignites, 
burning  with  a  blue  flame  and  evolving  fumes  of  SO 2  At  about  97° 
it  passes  over  into  the  monoclimc  phase  It  is  insoluble  in  water  and 
acids,  but  is  soluble  in  oil  of  turpentine,  carbon  bisulphide  and  chlo- 

There  are  few  minerals  that  are  apt  to  be  mistaken  for  sulphur. 
From  all  of  them  it  may  be  distinguished  by  its  bnttleness  and  by  the 
fact  that  it  melts  readily  and  burns  with  a  nonlummous  blue  flame 

Syntheses  — Crystals  with  the  form  of  the  mineral  are  produced  by 
the  evaporation  of  solutions  of  sulphur  in  carbon  bisulphide,  and  also 
by  sublimation  from  the  fumes  of  ore  roasters 

Occurrence  and  Origin  — Sulphur  occurs  most  abundantly  m  regions 
of  active  or  extinct  \olcanoes,  and  in  beds  associated  with  limestone 
and  gypsum  (CaSO*  2H20)  In  volcanic  regions  it  is  produced  by 
reactions  between  the  gases  emitted  from  the  volcanoes,  or  by  the  reac- 
tions of  these  with  the  oxygen  of  the  air  (seep  18)  The  deposits  in 
gypsum  beds  may  result  from  reduction  of  the  gypsum  by  organic 
matter.  Sulphur  is  formed  also  as  a  decomposition  product  of  sulphides 

In  Iceland  and  other  districts  of  hot  springs  sulphur  is  often  deposited 
in  the  form  of  powder  as  the  result  of  reactions  similar  to  those  that 
take  place  between  the  gases  of  volcanoes  These  hot  springs  are  always 
connected  with  dying  volcanoes,  being  frequently  but  the  closing 
stages  of  their  existence 

Localities — The  localities  at  which  sulphur  is  known  to  exist  are 
very  numerous  Those  of  commercial  importance  are  Girgenti  m  Sicily, 
Cadiz  in  Spam,  Japan,  and  in  the  United  States,  at  the  geysers 'of  the 
Napa  Valley,  Sonoma  County,  and  at  Clear  Lake,  Lake  County, 
California,  at  Cove  Creek,  Millard  County,  Utah,  at  the  mines  of  the 
Utah  Sulphur  Company  in  Beaver  County,  in  the  same  State,  at 
Thermopohs,  Wyoming,  and  at  various  hot  springs  in  Nevada  The 
mineral  occurs  also  abundantly  in  the  Yellowstone  National  Park,  but 
cannot  be  placed  on  the  market  because  of  high  transportation  charges 


Its  principal  occurrence  m  the  United  States  is  at  Lake  Charles  in 
Calcasieu  Parish,  La ,  where  it  impregnates  a  bed  of  limestone  at 
a  depth  of  from  450  to  1,100  feet  It  occurs  also  abundantly  in  the 
coastal  districts  of  Texas  Here  it  is  associated  with  gypsum 

Extraction  — Sulphur,  when  mined,  is  mixed  with  clay,  earth,  rock  and 
other  impurities  Until  recently  it  was  purified  by  piling  in  heaps  and 
igniting  A  portion  of  the  sulphur  burned  and  melted  the  balance, 
which  flowed  off  and  was  caught  A  purer  product  is  ob  tamed  by  dis- 
tillation "Flowers  of  Sulphur"  are  made  in  this  way  At  present 
much  of  the  sulphur  is  extracted  by  treating  the  impregnated  rock  m 
retorts  with  steam  under  a  pressure  of  60  pounds  and  at  a  temperature 
of  144°  C  The  sulphur  melts  and  flows  to  the  bottom  of  the  retorts 
from  which  it  is  drawn  off 

In  Louisiana  and  Texas,  superheated  steam  is  forced  downward  into 
the  sulphur-impregnated  rocks.  This  melts  the  sulphur,  which  con- 
stitutes about  70  per  cent  of  the  rock  mass  The  melted  sulphur  is 
forced  to  the  surface  and  caught  in  wooden  bins  The  crude  material 
has  a  guaranteed  content  of  over  99!  per  cent  sulphur 

Uses  — Sulphur,  or  brimstone,  is  used  m  the  manufacture  of  some 
kinds  of  matches,  m  making  gunpowder,  and  m  vulcanizing  rubber 
to  increase  its  strength  and  elasticity  It  is  used  extensively  in  the 
manufacture  of  sulphuric  acid,  but  is  rapidly  giving  way  to  pynte 
for  this  purpose  It  is  also  utilized  for  bleaching  straw,  in  the  man- 
ufacture of  certain  pigments,  among  \\hich  is  vermilion,  and  in  the 
preparation  of  certain  medicinal  compounds 

Production  — Most  of  the  domestic  product  is  at  present  from  the 
Calcasieu  Pansh,  La ,  where  about  300,000  tons  are  mined  annually. 
New  mines  have  been  opened  near  Thermopolis  in  Wyoming,  in  Bra- 
zona  County,  Texas,  and  at  Sulphur  Springs,  Ne\ada.  The  total 
amount  of  the  mineral  mined  in  1912  was  303,472  tons,  valued  at  $5,256,- 
422  Besides,  there  were  imported  about  29,927  tons  valued  at  $583,974, 
most  of  which  came  from  Japan  Sicily  is  the  largest  producer  of  the 
mineral,  extracting  about  400,000  tons  annually. 


The  arsenic  group  comprehends  metallic  arsenic,  antimony,  bismuth 
and  (according  to  some  mineralogists),  tellurium,  besides  compounds 
of  these  metals  with  each  other  They  all  crystallize  in  the  rhombo- 
hedral  division  of  the  hexagonal  system  (ditrigonal  scalenohedral  class). 
The  only  members  of  the  group  that  are  at  all  common  are  arsenic  and 


Arsenic  (As) 

Arsenic  is  rarely  found  in  crystals  It  usually  occurs  massive  or  in 
botryoidal  or  globular  forms 

Specimens  of  the  mineral  are  rarely  pure  They  usually  contain 
some  antimony,  and  traces  of  iron,  silver,  bismuth,  and  other  metals 

The  crystals  are  cubical  in  habit,  with  an  axial  ratio  of  i  .  i  4025 
The  principal  forms  observed  are  oR(oooi),  R(ioTi),  JR(ioT4), 
— |R(oil2)  and  —^(0332)  Twins  are  rare,  with  -|R(oil2)  the 
twinning  plane 

Arsenic  is  lead-gray  or  tin-white  on  fresh  fractures,  and  dull  gray  or 
nearly  black  on  surfaces  that  have  been  exposed  for  some  time  to  the 

Crystals  cleave  readily  parallel  to  the  base  The  fracture  of  massive 
pieces  is  uneven  The  mineral  is  brittle  Its  hardness  is  3  5  and  its 
density  5  6-5  7  Its  streak  is  tin-white  tarnishing  soon  to  dark  gray 
It  is  an  electrical  conductor 

Arsenic  may  easily  be  distinguished  from  nearly  all  other  minerals, 
except  antimony  and  some  of  the  rarer  metals,  by  the  color  of  its  fresh 
surfaces  From  these,  with  the  exception  of  antimony,  it  is  also  readily 
distinguished  by  its  action  on  charcoal  before  the  blowpipe,  when  it 
volatilizes  completely  without  fusing,  at  the  same  time  tmgeing  the 
flame  blue  and  giving  rise  to  dense  white  fumes  of  As20s,  which  coat  the 
charcoal  The  fumes  of  arsenic  possess  a  very  disagreeable  and  oppres- 
sive odor,  while  those  of  antimony  have  no  distinct  odor 

Syntheses  — Arsenic  has  been  obtained  in  crystals  by  subliming 
arsenic  compounds  protected  from  the  air  It  has  also  been  obtained  m 
the  wet  way  by  heating  realgar  (As2Sa)  with  sodium  bicarbonate  at 
300°  C 

Occurrence  and  Origin  — Arsenic  often  accompanies  ores  of  antimony, 
silver,  lead  and  other  metals  in  veins  in  crystalline  rocks,  especially  in 
their  upper  portions,  where  it  was  formed  by  reduction  from  its  com- 

Locahties  — The  silver  mines  at  Freiberg,  and  other  places  m  Saxony 
afford  native  arsenic  in  some  quantity  It  is  found  also  in  the  Harz,  at 
Zmeov  in  Siberia,  in  the  silver  mines  of  Chile  and  elsewhere. 

Within  the  boundaries  of  the  United  States  arsenic  occurs  only  in 
small  quantity  at  Haverhill,  N  H  ,  at  Greenwood,  Me ,  and  at  a  silver 
and  gold  mine  near  Leadville,  Colo 

Uses— Arsenic  is  used  only  in  the  forms  of  its  compounds  The 
native  metal  occurs  too  sparingly  to  be  of  commercial  importance. 


Most  of  the  arsenic  compounds  used  in  commerce  are  obtained  from 
smelter  fumes  produced  by  smelting  arsenical  copper  and  gold  ores 

Antimony  (Sb) 

Antimony  is  more  common  than  arsenic,  which  it  resembles  in  many 
respects  It  is  generally  found  in  lamellar,  radial  and  botryoidal  masses, 
though  rhombohedral  crystals  are  known 

Most  antimony  contains  arsenic  and  traces  of  silver,  lead,  iron  and 
other  metals 

Its  crystals  are  rhombohedral  or  tabular  in  habit,  and  have  an  axial 
ratio  of  a  :  c=i  .  i  3236  The  forms  observed  on  them  are  the  same 
as  those  on  arsenic  with  the  addition  of  ocP2(ii2o),  and  several 
rhombohedrons  Twinning  is  often  repeated  The  cleavage  is  perfect 
parallel  to  oP(oooi) 

Antimony  exhibits  brilliant  cleavage  surfaces  with  a  tin-white  color 
On  exposed  surfaces  the  color  is  dark  gray  The  mineral  differs  from 
arsenic  in  its  greater  density  which  is  6  65-6  72,  and  in  the  fact  that  it 
melts  (at  629°)  before  volatilizing  Its  fumes,  moreover,  are  devoid  of 
the  garlic  odor  of  arsenic  fumes 

Syntheses  — Crystals  of  antimony  are  often  obtained  from  the  flues  of 
furnaces  in  which  antimomal  lead  is  treated.  They  have  also  been 
made  by  the  reduction  of  antimony  compounds  by  hydrogen  at  a  high 

Occurrence  and  Localities  — Antimony  occurs  in  lamellar  concretions 
in  limestone  near  Sala,  Sweden,  and  at  nearly  all  of  the  arsenic  localities 
mentioned  above,  especially  in  veins  containing  stibnite  (Sb2Ss)  or  silver 
ores  It  is  found  also  in  fairly  large  quantities  in  veins  near  Fredencton, 
York  County,  New  Brunswick,  in  California  and  elsewhere 

Uses  — Although  the  metal  antimony  is  of  considerable  importance 
from  an  economic  point  of  view,  being  used  largely  in  alloys,  the  native 
mineral,  on  account  of  its  rarity,  enters  little  into  commerce  Some  of 
the  antimony  used  m  the  arts  is  produced  from  its  sulphide,  stibnite 
(see  p  72)  Most  of  the  metal,  however,  is  obtained  in  the  form  of  a 
lead-antimony  alloy  in  the  smelting  of  lead  ores  and  the  refining  of  pig 

Bismuth  (Bi)  is  usually  in  foliated,  granular  or  arborescent  forms, 
and  very  rarely  in  rhombohedral  crystals,  with  a  .  c=i  '  i  3036  It  is 
silver-white  with  a  reddish  tinge,  is  opaque  and  metallic  Its  streak  is 
white,  its  hardness  2-2  5  and  density  98  It  fuses  at  271°.  On  charcoal 
it  volatilizes  and  gives  a  yellow  coating  It  dissolves  in  HNOs  When 


this  solution  is  diluted  a  white  precipitate  results  The  mineral  occurs 
in  veins  with  ores  of  silver,  cobalt,  lead  and  zinc  It  is  of  no  commercial 
importance  Most  of  the  metal  is  obtained  in  the  refining  of  lead  In  1913 
the  United  States  produced  185,000  Ibs  and  Bolivia  about  606,000  Ibs 

Tellurium  (Te)  usually  occurs  in  prismatic  crystals  with  a  tin-white 
color  and  in  finely  granular  masses  in  veins  of  gold  and  silver  ores, 
especially  sulphides  and  tellundes     Its  hardness  is  2  and  density  6  2 
Before  the  blowpipe  it  fuses,  colors  the  flame  green,  coats  the  charcoal 
with  a  white  sublimate  bordered  by  led,  and  yields  white  fumes 

The  mineral  tellurium  is  of  little  value  as  a  source  of  the  metal 
Most  of  that  used  in  the  arts  is  obtained  as  a  by-product  in  the  elec- 
trolytic refining  of  copper  made  from  ores  containing  tellundes  and 
from  the  flue  dust  of  acid  chambers  and  smelting  furnaces  The  United 
States,  in  1913,  produced  about  10,000  Ibs  of  tellurium  and  selenium, 
valued  at  $3^,000 


The  metallic  elements  occur  as  minerals  m  comparatively  small  quan- 
tity, most  of  the  metals  used  in  the  industries  being  obtained  from  their 
compounds  Iron,  the  most  common  of  all  the  metals  used  in  com- 
merce, is  rare  as  a  mineral,  as  are  also  lead  and  tin  Silver,  copper,  gold 
and  platinum  are  sufficiently  important  to  be  included  in  our  list  for 
study  Gold  and  platinum  are  known  almost  exclusively  in  the  metallic 
state  A  large  portion  of  the  copper  produced  in  this  country  is  also 
native,  and  some  of  the  silver 

Silver,  copper,  lead,  gold,  mercury  and  the  alloys  of  gold  and  mer- 
cury crystallize  in  distinct  crystals  belonging  to  the  isometric  system 
(hexoctohedral  class)  Platinum,  as  usually  found,  is  in  small  plates 
and  grains  Crystals,  however,  have  been  described  and  they,  too,  are 
isometric  Platinum  and  iron  are  separated  from  the  other  metals  and, 
together  with  the  rare  alloys  of  platinum  with  indium  and  osmium,  are 
placed  in  a  distinct  group  which  is  dimorphous  The  reason  for  this  is 
that  platinum,  although  isometric  in  crystallization,  often  contains 
notable  traces  of  indium,  which  in  its  alloy  with  osmium  is  hexagonal 
(rhombohedral)  Indium,  thus,  is  dimorphous,  hence  platinum  which 
forms  crystals  with  it  and  is,  therefore,  isomorphous  with  it,  must  also 
be  regarded  as  dimorphous  The  various  platinum  metals  thus  com- 
pnse  an  isodimorphous  group  Iron  is  placed  in  the  same  group  because 
it  is  so  frequently  alloyed  with  platinum  The  metals  are,  therefore, 
divisible  into  two  groups,  one  of  which  comprises  the  metals  named  at 



the  beginning  of  this  paragraph  and  the  other  consists  of  the  rare  metals, 
palladium,  platinum,  indium,  osmium,  iron  and  their  alloys  The 
metal  tin,  which  is  tetragonal  m  its  native  condition,  constitutes  a  third 
group,  but  since  it  is  extremely  rare  it  will  not  be  referred  to  again 


This  group  embraces  the  native  metals,  copper,  siker,  gold,  gold- 
amalgam  (Au  Hg),  siher-amalgam  (Ag  Hg),  mercury,  and  leal  All 
crystallize  in  the  isometric  system  (hexoctahedral  class),  and  all  form 
twins,  with  0(in)  the  twinning  plane  Copper,  silver  and  gold  are 
the  most  important 

Copper  (Cu) 

Most  of  the  copper  of  commerce  is  obtained  from  one  or  the  other  of 
its  sulphides     A    large   portion,  however,   is 
found  native     This  occurs  m  tiny  grams  and 
flakes,    in    groups   of   crystals   and    in    large 
masses  of  irregular  shapes 

In  spite  of  its  softness  copper  is  better 
crystallized  than  either  gold  or  silver  It  is 
true  that  its  crystals  are  usually  flattened  and 
otherwise  distorted,  but,  nevertheless,  planes 

can  very  frequently  be  detected  upon  them 

rr.i         -          i  *  ,  -,  >v      /       \     FIG    2i.— Copper  Crystal 

The  principal  forms  observed  are  oo  O  oo  (100),      ^^  M  Q  *^        *     , 

oo  O(no),  0(ni),  and  various  tetrahexahedra      20  &  1 2io' (h). 

and  icositetrahedra.  (Figs.  21  and  22  )  Some- 
times the  crystals  are  sim- 
ple, in  other  cases  they  are 
twinned  parallel  to  O 
Often  they  are  skeleton 
crystals  Groups  of  crys- 
tals are  very  common 
These  possess  the  arbo- 
rescent forms  so  frequently 
seen  in  specimens  from 
Keweenaw  Point  in  Mich- 
igan, or  are  groupings  of 
simple  forms  extended  in 
the  direction  of  the  cubic 

FIG.  22. — Crystal  of  Copper  from  Keweenaw  Point, 
Mich ,  with  wO(iio)  and  202(211) 


Cbpper  is  very  ductile  and  very  malleable     Its  hardness  is  only 


2  5-3  and  its  density  about  88  It  possesses  no  cleavage,  and  its  frac- 
ture, like  that  of  the  other  metals,  is  hackly  In  color  it  is  copper-red 
by  reflected  light,  often  tarnishing  to  a  darker  shade  of  red  In  very 
thin  plates  it  is  translucent  with  a  green  color  The  metal  fuses  at 
1083°  and  easily  dissolves  in  acids  It  is  an  excellent  conductor  of  elec- 

Its  most  characteristic  chemical  reaction  is  its  solubility  in  nitric 
acid  with  the  evolution  of  brownish  red  fumes  of  nitrous  oxide  gas 

Copper  may  easily  be  distinguished  from  all  other  substances  except 
gold  and  a  few  alloys  by  its  malleability  and  color  It  is  distinguished 
from  gold  by  the  color  of  its  borax  bead  and  by  its  solubility  in  nitric 
acid  with  the  production  of  a  blue  solution  which  takes  on  an  intense 
azure  color  when  treated  with  an  excess  of  ammonia  From  the  alloys 
that  resemble  it,  copper  may  be  distinguished  by  its  greater  softness  and 
the  fact  that  it  yields  no  coatings  when  heated  on  charcoal,  while  at  the 
same  time  its  solution  in  nitric  acid  yields  the  reaction  described  above 

Syntheses  — Copper  crystals  separate  upon  cooling  solutions  of  the 
metal  in  silicate  magmas  and  upon  the  electrolysis  of  the  aqueous  solu- 
tions of  its  salts 

Occurrence  — The  principal  modes  of  occurrence  of  the  metal  are,  (i) 
as  fine  particles  disseminated  through  sandstones  and  slates,  (2)  as  solid 
masses  filling  the  spaces  between  the  pebbles  and  boulders  making  up 
the  rock  known  as  conglomerate,  (3)  in  the  cavities  in  old  volcanic  lavas, 
known  as  amygdaloid,  (4)  as  crystals  or  groups  of  crystals  imbedded  m 
the  calcite  of  veins,  (5)  in  quartz  veins  cutting  old  igneous  rocks  or 
schists,  and  (6)  associated  with  the  carbonates,  malachite  and  azurite, 
and  with  its  different  sulphur  compounds,  in  the  weathered  zone  of 
many  veins  of  copper  ores 

The  copper  that  occurs  in  the  upper  portions  of  veins  of  copper 
sulphides  is  plainly  of  secondary  origin  That  which  occurs  in  conglom- 
erates and  other  fragmental  rocks  and  in  amygdaloids  was  evidently 
deposited  by  water,  but  whether  by  ascending  magmatic  water  or  by 
descending  meteoric  water  is  a  matter  of  doubt 

Localities  — Native  copper  is  found  in  Cornwall,  England,  in  Nassau, 
Germany,  in  Bolivia,  Peru,  Chile  and  other  South  American  countries, 
in  the  Appalachian  region  of  the  United  States  and  in  the  Lake  Superior 
region,  both  on  the  Canadian  and  the  American  sides 

The  most  important  district  in  the  world  producing  native  copper  is 
on  Keweenaw  Point,  in  Michigan  The  mineral  occurs  mainly  in  a  bed 
of  conglomerate  of  which  it  constitutes  from  i  to  3  per  cent,  though  it  is 
found  abundantly  also  in  sandstone  and  in  the  amygdaloidal  cavities 


of  lavas  associated  with  the  conglomerates  Veins  of  caicite,  through 
which  groups  of  bright  copper  en  stals  are  scattered  are  also  very  plentiful 
in  many  parts  of  the  district  The  copper  is  nearh  always  mixed  with 
silver  in  visible  grains  and  patches 

Extraction  and  Refining  —The  rock  containing  the  native  metal  is 
crushed  and  the  metal  is  separated  from  the  useless  material  by  wash- 
ing The  concentrates,  consisting  of  the  crushed  metal  mixed  with 
particles  of  rock  and  other  impurities  are  then  refined  by  smelting 
methods  or  by  electrolysis 

Uses  —The  uses  of  copper  are  so  many  that  all  of  even  the  important 
uses  cannot  be  mentioned  in  this  place  Both  as  a  metal  and  in  the  form 
of  its  alloys  it  has  been  employed  for  utensils  and  war  implements  since 
the  earliest  times  In  recent  times  one  of  its  principal  uses  has  been  for 
the  making  of  telegraph,  telephone  and  trolley  wires  It  is  employed 
extensively  in  electroplating  by  all  the  great  newspapers  and  publishers, 
and  is  an  important  constituent  of  the  valuable  alloys  brass,  bronze, 
bell  metal  and  German  silver  Its  compound,  blue  vitriol  (copper  sul- 
phate), is  used  in  galvanic  batteries,  and  its  compounds  with  arsenic 
are  utilized  as  pigments 

Production — The  world's  production  of  copper  amounted  to  1,126,- 
ooo  tons  in  1912,  but  a  large  portion  of  this  was  obtained  from  its  car- 
bonates and  sulphides  The  quantity  obtained  from  the  native  metal  is 
unknown  The  contribution  of  the  United  States  to  this  total  was 
about  621,000  tons,  valued  at  about  $206,382,500,  of  which  115,000  tons 
was  native  copper  from  the  Lake  Superior  region  The  largest  single 
mass  ever  found  in  the  Lake  Superior  region  weighed  420  tons 

Silver  (Ag) 

Silver  is  usually  found  in  irregular  masses,  in  flat  scales,  in  fibrous 
dusters,  and  in  crystal  groups  with  arborescent  or  acicular  forms 
Sometimes  the  crystals  are  well  developed,  more  frequently  they  ex- 
hibit only  a  few  distinct  faces,  but  in  most  cases  they  are  so  distorted 
that  it  is  difficult  to  make  out  their  planes 

Pure  silver  is  unknown  The  mineral  as  it  is  usually  obtained  con- 
tains traces  of  gold,  copper,  and  often  some  of  the  rarer  metals,  depend- 
ing upon  its  associations. 

Ideally  developed  silver  crystals  are  rare  They  usually  show 
ooOoo(ioo),  006(110),  0(in)  various  tetrahexahedrons  and  other 
more  complicated  forms  The  majority  of  the  crystals  are  distorted  by 
curved  faces  and  rounded  edges,  and  many  of  them  by  flattening  or 


elongation  The  arborescent  groups  usually  branch  at  angles  of  60°, 
one  of  the  characteristic  angles  for  groups  of  isometric  crystals  Twins 
are  quite  common,  with  O(iii)  the  twinning  plane 

Silver  is  a  white,  metallic  mineral  when  its  surfaces  arc  clean  and 
fresh  As  it  usually  occurs  it  possesses  a  gray,  black  or  bluish  black 
tarnish  which  is  due  to  the  action  of  the  atmosphere  or  of  solutions 
The  tarnish  is  commonly  either  the  o\ide  or  the  sulphide  of  silvci 

The  mineral  has  no  cleavage  Its  fracture  is  hackly  II  is  soft 
(hardness  2-3),  malleable  and  ductile,  and  is  an  excellent  conductor 
of  heat  and  electricity  Its  density  is  about  10  5,  varying  slightly 
with  the  character  and  abundance  of  its  impurities  It  fuses  at 

It  is  readily  soluble  in  nitric  acid  forming  a  solution  from  which 
a  white  curdy  precipitate  of  silver  chloride  is  thrown  down  on  the 
addition  of  any  chloride  This  precipitate  is  easily  distinguished  from 
the  corresponding  lead  chloride  by  its  insolubility  in  hot  water 

Synthesis  — Crystals  bounded  by  0(in)  and  °o  0  oo  (100)  have  been 
made  by  the  reduction  of  silver  sulphate  solutions,  with  sulphurous 

Occurrence — Native  silver  is  found  in  veins  with  calcite  (CaCOO? 
quartz  (8102),  and  other  gangues  traversing  crystalline  rocks,  like 
granite  and  various  lavas,  and  also  in  veins  cutting  conglomerates 
and  other  rocks  formed  from  pebbles  and  sands  It  is  also  disseminated 
in  small  particles  through  these  rocks  It  occurs  invisibly  disseminated 
in  small  quantities  through  many  minerals,  particularly  sulphides, 
and  visibly  intermingled  with  native  copper  It  is  abundant  in  the  upper 
weathered  zones  of  many  veins  of  silver-bearing  ores,  and  m  the  zones 
of  secondary  enrichment  in  the  same  veins  It  also  occurs  in  small 
quantity  m  placers  In  general,  its  origin  is  similar  to  that  of  gold 
(see  p  59) 

Localities  — The  localities  in  which  silver  is  found  are  too  numerous 
to  mention  Andreasberg  in  the  Harz  has  produced  many  fine  crys- 
tallized specimens  The  principal  deposits  now  worked  are  at  Cobalt 
in  Canada,  in  Peru,  in  Idaho,  at  Butte,  Montana,  in  Arizona  and  at 
many  places  m  Colorado  On  Keweenaw  Point,  in  Michigan,  fine 
crystals  have  been  found  in  the  calcite  veins  cutting  the  copper-bearing 
rocks,  and  masses  of  small  size  in  the  native  copper  so  abundant  in  the 
district  Indeed  some  of  the  copper  is  so  rich  in  silver  that  the  ore 
was  in  early  times  mined  almost  exclusively  for  its  silver  content  At 
present  the  silver  is  recovered  from  the  copper  in  the  refining  process 
At  Cobalt  the  mineral  occurs  m  well  defined  veins  one  inch  to  one  foot 


or  more  in  width,  cutting  a  series  of  slightly  inclined  pre-Cambnan 
beds  of  fragmental  and  igneous  rocks  The  \eins  contain  native  silver, 
sulphides  and  arsenides  of  cobalt,  nickel,  iron  and  copper,  caicite  and  a 
little  quartz  Many  of  the  veins  are  so  rich  (Fig  23)  that  Cobalt  has 
become  one  of  the  most  important  camps  producing  native  silver  in 
the  world. 

Extraction  and  Refining — Silver  is  obtained  from  placers  in  small 
quantity  by  the  methods  made  use  of  in  obtaining  gold  (see  p  6i\ 
i  e ,  by  hydraulic  mining  When  it  occurs  in  quartz  veins  or  m  complex 
ores  such  as  constitute  the  oxidized  portion  of  ore-bodies,  the  mass 
may  be  crushed  and  then  treated  with  quicksilver,  which  amalgamates 
with  the  native  silver  and  gold,  forming  an  alloy.  Such  ores  are  known 

FIG.  23 — Plate  of  Silver  from  Confagas  Mine    Cobalt     Dimensions  32X14X1 
ins     Weight  37  Ibs.    (Photo  by  C  W.  Knight ) 

as  free  milling  The  silver  is  freed  from  the  gold  and  other  metals  by 
a  refining  process.  It  is  separated  from  native  copper  by  electrolytic 

Uses  — Silver  is  used  in  the  arts  to  a  very  large  extent  Jewelry, 
ornaments,  tableware  and  other  domestic  utensils,  chemical  apparatus 
and  parts  of  many  physical  instruments  are  made  of  it  It  is  used  also 
in  the  production  of  mirrors  and  in  the  manufacture  of  certain  compounds 
used  in  surgery  and  in  photography  Its  alloy  with  copper  forms  the 
staple  coinage  of  China,  Mexico  and  most  of  the  South  American  coun- 
tries, and  the  subsidiary  (or  small)  coinage  of  most  countries  In 
the  United  States  it  is  used  in  the  coinage  of  silver  dollars  and  of  frac- 
tions of  the  dollar  as  small  as  the  dime.  The  silver  corns  of  the  United 
States  are  nine-tenths  silver  and  one-tenth  copper,  the  latter  metal  being 
added  to  give  hardness  English  corns  contain  i2|  parts  silver  to  one 


part  of  copper     In  1912  the  world's  coinage  of  silver  consumed  161,- 
763,415  02 ,  with  a  value  after  coinage  of  $171,293,000 

Production —The  total  production  of  silver  in  the  United  States 
during  1912  was  over  63,766,000  oz ,  valued  at  over  $39,197,000,  of 
which  about  $100,000  worth  came  from  placers  and  $325,000  worth 
from  the  copper  mines  of  Michigan  The  balance  was  obtained  by 
smelting  silver  compounds  and  in  the  refining  of  gold,  lead,  copper  and 
zinc  ores  The  world's  production  of  silver  during  1912  was  224,488,- 
ooo  oz ,  valued  at  over  $136,937,000,  but  most  of  this  was  obtained 
from  the  compounds  of  silver  and  not  from  the  native  metal  The 
proportion  obtained  from  the  mineral  is  not  definitely  known,  but  the 
production  of  Canada  was  more  than  30,243,000  oz ,  valued  at 
$17,672,000  and  nearly  all  of  this  came  from  Cobalt,  where  the  ore  is 
native  silver 

Gold  (Au) 

A  large  portion  of  the  gold  of  the  world  has  been  obtained  m  the 
form  of  native  metal  The  greater  portion  of  the  metal  is  so  very  finely 
disseminated  through  other  minerals  that  no  sign  of  its  presence  can  be 
detected  even  with  high  powers  of  the  microscope  Although  present 
in  such  minute  quantities  it  is  very  widely  spread,  many  rocks  con- 
taining it  jn  appreciable  quantities  Its  visible  grains,  as  usually  found, 
are  little  rounded  particles  or  thin  plates  or 
scales  mixed  with  sand  or  gravel,  or  tiny 
irregular  masses  scattered  through  white  vem- 

Native  gold  rarely  occurs  in  well  formed 
crystals     The  metal  is  so  soft  that  its  crystals 
are  battered  and  distorted  by  very  slight 
pressure.    Occasionally  well  developed  crys- 
tals,  bounded  by  octahedral,   dodecahedral 
FIG  24  -Octahedral  Skele-    and  compllcated  icositetrahcdral  and    tetra- 
ton  Crystal  of  Gold  with    ,_,,,-  ,      t 

Etched  Faces  hexahedral   faces  are  met  with,  but  usually 

the  crystals  are  elongated  or  flattened  Skele- 
ton crystals  (Fig.  24)  and  groups  of  crystals  are  more  frequently  found 
than  are  simple  crystals.  Twins  are  common,  with  O(iii)  the  twin- 
ning plane 

As  found  in  nature,  gold  is  frequently  alloyed  with  silver  and  it 
often  contains  traces  of  iron  and  copper  and  sometimes  small  quanti- 
ties of  the  rarer  metals 

Gold  containing  but  a  trace  of  silver  up  to  1 6  per  cent  of  this  metal 


is  known  simply  as  gold  When  the  percentage  of  silver  present  is 
larger  it  is  said  to  be  argentiferous  When  the  percentage  reaches 
20  per  cent  or  above  the  alloy  is  called  clectru  ,:  Palladium,  rhodium 
and  bismuth  gold  are  alloys  of  the  last-named  metal  roth  the  rare  metals 
palladium  or  rhodium  or  with  the  more  common  bismath 

The  color  of  the  different  varieties  of  the  mineral  varies  from  pinkish 
silver-white  to  almost  copper-red  Pure  gold  is  golden  yellow  With 
increase  cf  silver  it  becomes  lighter  in  color  and  T\ith  increase  in  copper, 
darker  The  rich  red-yellow  ot  much  of  the  gold  used  in  the  arts  is  due 
to  the  admixture  ot  copper  In  very  thin  plates  or  lea\  es  ( ooi  mm  ) 
gold  is  translucent  \\ith  a  blue  or  green  tint 

Gold  is  soft,  malleable  and  ductile  Its  luster  is,  of  course,  metallic 
and  its  streak,  yellow  When  pure  its  density  is  1943,  its  hardness 
between  2  and  3,  and  its  fusing  point  1062°  The  metal  is  insoluble  in 
most  acids,  but  it  is  readily  dissolved  in  a  mixture  of  nitric  and  hydro- 
chloric acids  (aqua  regia)  It  is  not  acted  upon  by  water  or  the  atmos- 
phere Its  negative  properties  distinguish  it  from  the  other  substances 
-which  it  resembles  in  appearance  It  is  a  good  conductor  of  electricity. 

Syntheses  — Crystals  of  gold  have  been  obtained  by  heating  a  solu- 
tion of  AuCls  in  amyl  alcohol,  and  by  treating  an  acid  solution  of  the 
same  compound  with  formaldehyde 

Occurrence — Native  gold  is  tound  in  the  quartz  of  veins  cutting 
through  granite  and  schistose  rocks,  or  in  the  gravels  and  sands  of  rivers 
whose  channels  cut  through  these,  and  in  the  sands  of  beaches  bordering 
gold-producing  districts  It  is  sometimes  found  in  the  compacted 
gravels  of  old  river  beds,  in  a  rock  known  as  conglomerate,  and  in  sand- 
stones It  is  also  present  in  small  quantities  in  many  volcanic  rocks, 
and  is  disseminated  through  pyrite  (FeS2)  and  some  other  sulphur  com- 
pounds and  their  oxidation  products 

The  gold  in  quartz  veins  occurs  as  grains  and  scales  scattered  through 
quartz  irregularly,  often  in  such  small  particles  as  to  be  invisible  to  the 
naked  eye,  or  as  aggregates  of  crystals  in  cavities  in  the  quartz  Pyrite 
is  nearly  always  associated  with  the  gold.  On  surfaces  exposed  to  the 
weather  the  pyrite  rusts  out  and  stains  the  quartz,  leaving  it  cavernous 
or  cellular 

Most  of  the  world's  supply  of  gold  has  come  from  placers.  These 
are  accumulations  of  sand  or  gravel  in  the  beds  of  old  river  courses 
The  sands  of  modern  streams  often  contain  considerable  quantities  of 
gold  Many  of  the  older  streams  were  much  larger  than  the  modern 
ones  draining  the  same  regions  and,  consequently,  their  beds  contain 
more  gold  This  was  originally  brought  down  from  the  mountains  or 


highlands  in  which  the  streams  had  their  sources  The  sands  and 
gravels  were  rolled  along  the  streams'  bottoms  and  their  greater  portion 
was  swept  away  by  the  currents  into  the  lowlands  The  gold,  however, 
being  much  heavier  than  the  sands  and  pebble  grains,  merely  rolled 
along  the  bottoms,  dropping  here  and  there  into  depressions  from  which 
it  could  not  be  removed  As  the  streams  contracted  in  volume  the  gold 
grains  were  covered  by  detritus,  or  perhaps  a  lava  stream  flowing  along 
the  old  river  channel  buried  them  These  buried  river  channels  with 
their  stores  of  sands,  gravels  and  gold  constitute  the  placers  With  the 
gold  are  often  associated  zircon  crystals,  garnets,  diamonds,  topazes 
and  other  gem  minerals  Alluvial  gold  is  usually  in  flattened  scales  or 
in  aggregates  of  scales  forming  nuggets  Some  of  the  nuggets  are  so 
large,  190  pounds  or  more  in  weight,  that  it  is  thought  they  may  have 
been  formed  by  some  process  of  cementation  after  they  were  transported 
to  their  present  positions 

The  gold-quartz  veins  are  usually  closely  associated  with  igneous 
rocks,  but  the  veins  themselves  may  cut  through  sedimentary  beds  or 
crystalline  schists  The  veins  are  supposed  to  have  been  filled  from 
below  by  ascending  solutions  Metallic  gold  is  also  present  m  the  oxi- 
dized zones  of  many  veins  of  gold-bearing  sulphides  and  m  the  zones  of 
secondary  enrichment  At  the  surface  the  iron  sulphides  are  oxidized 
into  sulphates,  leaving  part  of  the  gold  m  the  metallic  state  and  dissolv- 
ing another  part  which  is  carried  downward  and  precipitated 

Principal  Localities  — Vein  gold  occurs  m  greater  or  less  quantity  in 
all  districts  of  crystalline  rocks  It  has  been  obtained  m  large  quantity 
along  the  eastern  flanks  of  the  Ural  Mountains,  this  having  been  the 
most  productive  region  in  the  world  between  the  years  1819  and  1849 
It  has  been  obtained  also  from  the  Altai  Mountains  in  Siberia,  from  the 
mountains  m  southeastern  Brazil,  from  the  highlands  of  many  of  the 
Central  and  South  American  countries,  and  from  the  western  portion  of 
the  United  States,  more  particularly  from  the  western  slopes  of  the  Sierra 
Nevada  Mountains  and  the  higher  portions  of  the  Rocky  Mountains 
In  recent  years  auriferous  quartz  veins  have  been  worked  at  various 
points  m  Alaska,  at  Porcupine,  Ontario,  and  other  points  in  Canada 

The  great  placer  mines  of  the  world  are  in  California,  Australia  and 
Alaska  In  Australia  the  principal  gold  mines  are  situated  m  the  streams 
rising  in  the  mountains  of  New  South  Wales  and  their  extension  into 
Victoria  The  valleys  of 'the  Yukon  and  other  rivers  m  Alaska  have 
lately  attracted  much  attention,  and  in  the  past  few  years  the  beach 
sands  off  Nome  have  yielded  much  of  the  metal 

The  most  important  production  at  present  is  from  South  Africa 


where  the  metal  occurs  in  an  old  conglomerate  In  the  opinion  of  some 
geologists  this  is  an  old  beach  deposit,  in  the  opinion  of  others  the  gold 
was  introduced  into  the  conglomerate  long  after  it  had  consolidated 

The  sands  of  many  streams  in  Europe  and  in  the  eastern  United 
States  have  for  many  years  been  "panned"  or  cashed  for  gold  The 
South  Atlantic  States,  before  the  discovery  of  gold  m  California,  in 
1849,  yielded  annually  about  a  million  dollars'  worth  of  the  precious 
metal  All  of  it  was  obtained  by  working  the  gra\  els  and  sands  of  small 
rivers  and  rivulets  Many  of  these  streams  have  been  worked  o\er 
several  times  at  a  profit  and  the  mining  continues  to  the  present  day 
Small  quantities  of  gold  have  also  been  obtained  from  streams  in  Maine, 
New  Hampshire,  Maryland  and  other  Atlantic  coast  states 

Extraction  and  Refining — Gold  is  extracted  from  alluvial  sands 
and  from  placers  by  washing  in  pans  or  troughs  The  sand,  gravel 
and  foreign  particles  are  carried  away  by  currents  of  water  and 
the  gold  settles  down  with  other  heavy  minerals  to  the  bottom  of  the 
shallow  pans  used  in  hand  washing,  or  into  compartments  prepared  for 
it  in  troughs  when  the  processes  are  on  a  larger  scale  It  is  after- 
ward collected  by  shaking  it  with  mercury  or,  quicksilver,  m  \\hich  it 
dissolves  The  quicksilver  is  finally  driven  off  by  heat  and  the  gold 
left  behind  Auriferous  beach  sands  and  many  lake,  swamp  and  mer 
sands  are  dredged,  and  the  sand  thus  raised  is  treated  by  similar  methods 
Sands  containing  as  low  as  15  cents'  worth  of  metal  per  cubic  yard  can 
be  worked  profitably  under  f a\  orable  conditions 

Where  the  gold  occurs  free  (not  disseminated  through  sulphides) 
in  quartz  the  rock  is  crushed  to  a  fine  pulp  -with  -water  and  the  mixture 
allowed  to  flow  over  copper  plates  coated  \uth  quicksilver  The  gold 
unites  with  the  quicksilver  and  forms  an  alloy  from  which  the  mercury 
is  driven  off  by  heat  The  process  of  forming  allo}s  of  silver  or  gold 
with  mercury  is  known  as  amalgamation 

When  the  gold  is  disseminated  through  sulphides,  these  are  concen- 
trated, i  e ,  freed  from  the  gangue  material  by  washing  and  then 
roasted  This  liberates  the  gold  which  is  collected  by  amalgamation, 
or  is  dissolved  by  chlorine  or  cyanide  solutions  and  then  precipitated 

Uses  — Gold,  like  silver,  is  used  in  the  manufacture  of  jewelry  and  or- 
naments, in  the  manufacture  of  gold  leaf  for  gilding  and  in  the  produc- 
tion of  valuable  pigments  such  as  the  "purple  of  Cassms  "  It  also  con- 
stitutes the  principle  medium  for  coinage  in  nearly  all  of  the  most 
important  countries  of  the  world  The  gold  coins  of  the  United  States 
contain  900  parts  gold  in  1,000.  Those  of  Great  Britain  contain  916  66 
parts,  the  remaining  parts  consisting  of  copper  and  silver  The  total 


gold  coinage  of  the  United  States  mints  from  the  time  of  their  organi- 
zation to  the  end  of  the  year  1912  amounted  to  $2,765,900,000  The 
gold  coined  in  the  world's  mints  in  1912  amounted  m  value  to  $360,- 
671,382,  and  that  consumed  in  arts  and  industries  to  $174,100,000 
Jewelers  estimate  the  fineness  of  gold  in  carats,  24-carat  gold  being  pure 
Eighteen-carat  gold  is  gold  containing  18  parts  of  pure  gold  and  6  parts 
of  some  less  valuable  metal,  usually  copper  The  copper  is  added  to 
increase  the  hardness  of  the  metal  and  to  give  it  a  darker  color  The 
gold  used  most  in  jewelry  is  14  or  12  carats  fine 

Production — The  total  value  of  the  gold  product  of  the  United 
States  during  1912  was  $93,451,000  Of  this  the  following  states  and 
territories  were  the  largest  producers 

Alaska  $17,198,000        Nevada  $13,576,000 

California  20,008,000        South  Dakota  7,823,000 

Colorado  18,741,000        Utah  4,312,000 

Of  the  total  product,  placers  gelded  gold  valued  at  $23,019,633,  and 
quaitz  veins,  metal  valued  at  $62,112,000  The  balance  of  the  gold  was 
obtained  from  ores  mined  mainly  for  other  metals,  and  in  these  it  is 
probably  not  in  the  metallic  state  Moreover,  some  of  the  ore  in  quartz 
veins  is  a  gold  telluride,  but  by  far  the  greater  portion  of  the  product 
from  the  quartz  veins  and  placers  was  furnished  by  the  native  metal 

The  world's  yield  of  the  precious  metal  in  1912  was  valued  at  $466,- 
136,100  The  principal  producing  countries  and  the  value  of  the  gold 
produced  by  each  were 

South  Africa  $211,850,600  Mexico  $24,450,000 

United  States  93,45 1,500  India  11,055,700 

Australasia  54,509,400  Canada  12,648,800 

Russia  22,199,000  Japan  4,467,000 

Lead  occurs  very  rarely  as  octahedral  or  dodecahedral  crystals, 
in  thin  plates  and  as  small  nodular  masses  in  districts  containing  man- 
ganese and  lead  ores  and  also  in  a  few  placers  It  usually  contains 
small  quantities  of  silver  and  antimony  The  native  metal  ha1}  the 
same  properties  as  the  commercial  metal  Its  hardness  13  i  5  and 
density  113  It  melts  at  about  33  5° 

The  mineral  is  of  no  commercial  importance  The  metal  is  obtained 
from  galena  and  other  lead  compounds 

Mercury  occurs  as  small  liquid  globules  in  veins  of  cinnabar  (HgS) 
from  which  it  has  probably  been  reduced  by  organic  substances,  and  ift 


the  rocks  traversed  by  these  veins  The  native  metal  possesses  the 
same  properties  as  the  commercial  metal  It  solidifies  at  —  39°,  when 
it  crystallizes  in  octahedrons  ha\mg  a  cubic  cleavage  Its  density  is 
13  6  Its  boiling-point  is  350° 

The  commercial  metal  is  obtained  from  cinnabar  (p  98). 

Amalgam  (Ag  Hg)  is  found  in  dodecahedral  crystals  in  a  few  places, 
associated  with  mercury  and  silver  ores  It  occurs  also  as  embedded 
grams,  m  dense  masses  and  as  coatings  on  other  minerals  It  is  silver- 
white  and  opaque  and  gives  a  distinct  silver  streak  when  rubbed  on 
copper  Its  hardness  is  about  3  and  its  density  13  9  When  heated 
in  the  closed  tube  it  yields  a  sublimate  of  mercury  and  a  residue  of 
silver  On  charcoal  the  mercury  volatilizes,  leaving  a  silver  globule, 
soluble  in  nitric  acid 


The  platinum-iron  group  of  minerals  may  be  divided  into  the  plati- 
num and  the  iron  subgroups  The  latter  compnses  only  iron  and  nickel- 
it  on,  both  of  which  are  extremely  rare,  and  the  former,  the  metals 
platinum,  indium,  osmium,  ruthenium,  rhodium,  and  palladium  The 
platinum  metals  probably  constitute  an  isodimorphous  group  since 
they  occur  together  in  alloys,  some  of  which  are  isometric  and  others 
hexagonal  (rhombohedral)  Platinum  is  the  only  member  of  the  group 
of  economic  importance. 

Platinum  (Pt) 

Platinum  occurs  but  rarely  in  crystals  It  is  almost  universally 
found  as  granular  plates  associated  with  gold  in  the  sands  of  streams 
and  rivers,  and  rarely  as  tiny  grains  or  flakes  in  certain  very  basic 
igneous  rocks 

As  found  in  nature  the  metal  always  contains  iron,  indium,  rhodium, 
palladium  and  often  other  metals.  A  specimen  from  California  yielded: 

Pt       Au      Fe        Ir       ^Rh       Pd      Cu       IrOs    Sand     Total 
85  50       80     6  75     i  05     i  oo       60      i  40      i  10     2  95    101  15 

Though  the  metal  occurs  usually  in  grains  and  plates,  nevertheless 
its  crystals  are  sometimes  found.  On  them  cubic  faces  are  the  most 
prominent  ones,  though  the  octahedrons,  the  dodecahedrons  and 
tetrahexahedrons  have  also  been  identified  Like  the  crystals  of  silver 
and  gold,  those  of  platinum  are  frequently  distorted. 


The  color  of  platinum  is  a  little  more  gray  than  that  of  silver  Its 
streak  is  also  gray  Its  hardness  is  4-4  5  and  density  14  to  19  Pure 
platinum  has  a  density  of  21  5  It  is  malleable  and  ductile,  a  good 
conductor  of  electricity,  and  it  is  infusible  before  the  blowpipe  except 
in  very  fine  wire  It  is  not  dissoh  ed  by  any  single  acid,  though  soluble, 
like  gold,  in  aqua  regia  Its  melting  temperature  is  1755° 

Syntheses  —Crystals  have  been  obtained  by  cooling  siliceous  mag- 
mas containing  the  metal,  and  by  dissolving  the  metal  in  saltpelei  and 
cooling  the  mixture 

Occurrence — Platinum  is  found  in  the  sands  of  rivers  or  beaches 
and  in  placer  deposits  in  which  it  occurs  in  flattened  scales  or  in 
small  grains  Nuggets  of  considerable  size  are  sometimes  met  with, 
the  largest  known  weighing  about  iSf  kilos  It  is  present  also  in 
small  quantity  in  certain  very  basic  igneous  rocks,  like  pendotite 

Localities — It  occurs  m  nearly  all  auriferous  placer  districts  and 
in  small  quantities  in  the  sands  of  many  rivers,  among  them  the  Ivalo 
in  Lapland,  the  Rhine,  the  rivers  of  British  Columbia,  and  of  the  Pacific 
States  It  is  more  abundant  in  the  Natoos  Mountains  in  Borneo,  on 
the  east  flanks  of  the  Ural  Mountains  in  Siberia,  in  the  placer  of  an 
old  river  in  New  South  Wales,  Australia,  and  the  sands  of  rivers  of 
the  Pacific  side  of  Colombia  It  is  nearly  always  associated  with 
chromite  (p  200)  A  recent  discovery  which  may  prove  to  be  of  con- 
siderable importance  is  near  Goodsprmgs,  Nev ,  where  platinum  is  in 
the  free  state  associated  with  gold  in  a  siliceous  oie 

The  native  metal  is  probably  an  original  constituent  of  some  pen- 
dotites  (basic  igneous  rocks)  Its  presence  m  placers  is  due  to  the 
disintegration  of  these  rocks  by  atmospheric  agencies 

Extraction  and  Refimng  — The  metal  is  separated  from  the  sand 
with  which  it  is  mixed  by  washing  and  hand  picking  The  metallic 
powder  is  then  refined  by  chemical  methods 

Uses  — On  account  of  its  infusibihty  and  its  power  to  resist  the  coi- 
rosion  of  most  chemicals  the  metal  is  used  extensively  for  ciuciblcs 
and  other  apparatus  necessary  to  the  work  of  the  chemist  It  is  also 
used  by  dentists  and  by  the  manufacturers  of  incandescent  electric 
lamps  It  is  an  important  metal  in  the  manufactuie  of  physical  and 
certain  surgical  instruments,  and  was  formerly  used  by  Russia  for  coin- 
age The  most  important  use  of  the  metal  in  the  industries  is  in  the 
manufacture  of  sulphuric  acid  Sulphur  dioxide  (SCb)  and  steam  when 
mixed  and  passed  over  the  finely  divided  metal  unite  and  foim  HjSOi 
More  than  half  of  the  acid  made  at  present  as  manufactured  by  this 



Production  — Most  of  the  platinum  of  the  world  is  obtained  from 
placers  in  the  Urals  in  Russia  A  small  quantity  is  washed  from  the 
sands  of  gold  placers  in  Colombia,  Oregon  and  California,  and  an  even 
smaller  quantity  is  obtained  during  the  refining  of  copper  from  the  ores 
of  certam  mines  The  total  production  of  the  world  in  1912  was 
314,751  oz  The  output  for  Russia  m  this  year  was  about  300,000  oz  , 
of  Colombia  about  12,000  oz ,  and  of  the  United  States  721  oz  (equiv- 
alent to  505  02  of  the  refined  metal,  valued  at  $22,750)  In  addition, 
about  1,300  oz  were  obtained  m  the  refining  of  copper  bullion  imported 
from  Sudbury,  Ont ,  and  m  the  treatment  of  concentrates  from  the 
New  Rambler  Mine,  Wyoming  Of  this  about  500  oz  were  produced 

pIG    35 — iron  Meteorite  (Sidente)  from  Canyon  Diablo,  Arizona     Weight  265 
Ibs     (Field  Columbian  Museum  ) 

from  domestic  ores     The  importations  into  the  United  States  for  the 
same  year  were  about  125,000  oz  ,  valued  at  $4,500,000 

Platinum-iron,  or  iron-platinum  (Pt  Fe),  contains  from  10  per  cent 
to  19  per  cent  Fe  It  is  usually  dark  gray  or  black  and  is  magnetic  It 
is  found  with  platinum  m  sands  of  the  rivers  in  the  Urals  Its  crystals 
are  isometric 

Iron  (Fe)  occurs  in  small  grains  and  large  masses  in  the  basalt  at 
Ovifak,  Disko  Island,  W  Greenland,  and  at  a  few  other  points  in  Green- 
land, and  alloys  consisting  mainly  of  iron  are  found  in  the  sands  of  some 
rivers  in  New  Zealand,  Oregon  and  elsewhere  The  native  metal  always 
contains  some  nickel  The  most  common  occurrence  of  iron,  however,  is 
m  meteorites  (Fig  25)  In  these  bodies  also  it  is  aUoyed  with  Ni  When 



polished  and  treated  with  nitric  acid,  surfaces  of  meteoric  iron  exhibit 
penes  of  lines  (Widmanstatten  figures),  that  are  the  edges  of  plates  of 
different  composition  (Fig  26)  These  are  so  arranged  as  to  indicate 
that  the  substance  crystallizes  in  the  isometric  system 

Iridium  (Ir  Pt)  and  platin-iridium  (Pt  Ir)  are  alloys  of  indium  and 
platinum  found  as  silver- white  grains  with  a  yellowish  tinge,  associated 
with  platinum  in  the  sands  of  rivers  in  the  Urals,  Burmah  and  Brazil 
Their  hardness  is  6  to  7,  and  density  22  7  The  mineral  is  isometric 
and  its  fusing  point  is  between  2i5o°-225o°. 

FIG    26 — Widmanstatten  Figures  on  Etched  Surface  of  Meteorite  from  Toluca, 
Mexico     (One-half  natural  size )     (Field  Columbian  Mit\cntn  ) 

Palladium  (Pd)  is  usually  alloyed  with  a  little  Pb  and  Ir  It  is 
found  in  small  octahedrons  and  cubes  and  also  in  radially  fibrous  grams 
in  the  platinum  sands  of  Brazil,  the  Urals  and  a  few  other  places  It  is 
whitish  steel-gray  in  color,  has  a  hardness  of  4  to  5  and  a  density  of 
ii  3  to  ii  8  It  fuses  at  about  1549°  Its  crystallization  is  isometric 
About  2,390  oz  of  the  metal  were  produced  in  the  United  States  during 
1912,  but  all  of  it  was  obtained  during  the  refining  of  bullion.  The 
imports  were  4,967  oz ,  valued  at  $213,397 

Allopalladium  (Pd)  is  probably  a  dimorph  of  palladium  It  is  found 
in  six-sided  plates  that  are  probably  rhombohedral,  intimately  asso- 
ciated with  gold,  at  Tilkerode,  Harz 


Osmiridium  (Os  Ir)  and  mdosmine  (Ir  Os)  are  foundm  crystals  and 
flattened  grams  and  plates  that  are  apparently  rhombohedral  They 
consist  of  Ir  and  Os  m  different  proportions,  often  with  the  addition 
of  rhodium  and  ruthenium  Osmiridium  is  tin-white  and  iridosrmne 
steel-gray  Their  hardness  is  6  to  7  and  density  19  to  21  When  heated 
with  KNOs  and  KOH,  both  yield  the  distinctive  chlorine-like  odor  of 
osmium  o\ide  (Os04)  and  a  green  mass,  \\hich,  when  boiled  with 
water,  leaves  a  residue  of  blue  indium  oxide  Both  are  insoluble  in 
concentrated  aqua  regia  They  occur  \\ith  platinum  in  the  sands  of 
rivers  m  Colombia,  Brazil,  California,  the  Urals,  Borneo,  New  South 
Wales,  and  a  few  other  places  They  are  distinguished  from  platinum 
by  greater  hardness,  light  color  and  insolubility  in  strong  aqua  regia 

The  world's  product  of  refined  indium  is  about  5,000  oz ,  of  which 
the  United  States  furnishes  about  500  oz  Its  value  is  $63  per  oz 
Imports  into  the  United  States  during  1911  were  3,905  oz,  valued  at 
$210,616  The  sources  of  the  metal  are  native  indium,  osrniridmm, 
platinum,  copper  ore  and  bullion  The  metal  is  obtained  from  the  last 
two  sources  in  the  refining  process 



THE  sulphides  are  combinations  of  the  metals,  or  of  elements  acting 
like  bases,  with  sulphur  They  may  all  be  regarded  as  derivatives  of 
hydrogen  sulphide  (H2S)  by  the  replacement  of  the  hydrogen  by  some 
metallic  element  The  tellundes  are  the  corresponding  compounds  of 
EfeTe,  and  the  selemdes  of  EkSe 

With  the  same  group  are  also  placed  the  arsenides  and  the  anti- 
monides,  derivatives  of  HsAs  and  HsSb,  because  arsenic  and  antimony 
so  often  replace  m  part  the  sulphur  of  the  sulphides,  forming  with  these 
isomorphous  mixtures 

The  minerals  described  in  this  volume  may  be  separated  into  the 
following  groups  and  subgroups 

I  The  sulphides,  tellundes  and  selemdes  of  the  metalloids  arsenic, 
antimony,  bismuth  and  molybdenum 

II  The  sulphides,  tellundes,  selemdes,  arsenides  and  antimonides 
of  the  metals 

(a)  The  monosulphides,  etc     (Derivatives  of  HsS,  HgSe,  HsTe, 

H3As,  H3Sb ) 
(&)  The  disulphides,  etc     (Derivatives  of  2HsS,  2H2Te,  2HsAs, 


All  sulphur  compounds  when  mixed  with  dry  sodium  carbonate 
(Na2COs)  and  heated  to  fusion  on  charcoal  yield  a  mass  containing 
sodium  sulphide  (Na2$)  If  the  mass  is  removed  from  the  charcoal, 
placed  on  a  bright  piece  of  silver  and  moistened  with  a  drop  or  two  of 
water  or  hydrochloric  acid,  the  solution  formed  will  stain  the  silver  a 
dark  brown  or  black  color  (AgsS),  which  will  not  rub  off  The  sulphides 
yield  the  sulphur  reaction  when  heated  with  the  carbonate  on  platinum 
foil,  the  sulphates  only  when  charcoal  or  some  other  reducing  agent  is 
added  to  the  mixture  before  fusing  Moreover,  the  sulphides  yield 
sulphureted  hydrogen  when  heated  with  hydrochloric  acid,  while  the 
sulphates  do  not.  These  tests  are  extremely  delicate.  By  the  aid  of 


the  first  one  the  sulphur  in  any  compound  may  be  detected  By  the 
aid  of  the  others  the  sulphates  may  be  distinguished  from  the 

The  selemdes  are  recognized  by  the  strong  odor  evolved  \\hen  heated 
before  the  blowpipe  Selenates  and  selemtes  give  their  odor  only  after 
reduction  with  Na2COs 

The  tellundes,  \\hen  wanned  with  concentrated  HoSO-t,  dissolve  and 
yield  a  carmine  solution  from  which  water  precipitates  a  black  gray 
powder  of  tellurium 

All  substances  containing  arsenic  and  antimony  yield  dense  white 
fumes  when  heated  on  charcoal  in  the  oxidizing  flame  The  fumes  of 
arsenic  possess  a  characteristic  odor  while  those  of  antimony  are  odorless 
When  heated  in  the  open  tube,  arsenides  and  compounds  \\ith  sulphur 
and  arsenic  yield  a  very  volatile  sublimate  composed  of  tiny  white  crys- 
tals (AS203)  The  corresponding  sublimate  for  antimomdes  and  for 
compounds  with  antimony  and  sulphur  is  nonvolatile,  or  difficultly 
volatile,  and  apparently  amorphous  It  is  usually  found  on  the  under 
side  of  the  tube 


The  sulphides  of  the  metalloids  include  compounds  of  sulphur  with 
arsenic,  antimony,  bismuth  and  molybdenum  and  a  selemde  and  several 
tellundes  of  bismuth  Only  the  sulphides  are  of  importance.  One, 
shbmte  (Sb2Ss),  is  utilized  as  a  source  of  antimony 

Realgar  (As2S2) 

Realgar  occurs  as  a  bright  red  incrustation  on  other  substances, 
as  compact  and  granular  masses  and  as  crystals  implanted  on  other 
minerals  It  is  usually  associated  with  the  bright  yellow  orpunent 

(P  7i) 

Absolutely  pure  realgar  should  have  the  following  composition 

As,  70  i  per  cent,  S,  29  9  per  cent  The  mineral,  however,  usually 
contains  a  small  amount  of  impurities  It  may  be  looked  upon  as  a 
derivative  of  H2S  in  which  the  hydrogen  of  two  molecules  is  replaced 
by  two  arsenic  atoms,  thus* 

H2S  As=S 

yielding   | 
H2S  As=S, 



oo  P  5b  ,  oio  (b) ,  oP,  ooi 
(c),  Poo,  on  (q)  and  P, 
in  M 

Crystals  of  realgar  are  usually  short  and  prismatic  m  habit  They 
are  monoclmic  (prismatic  class)  with  an  axial  ratio  a  b  c  =i  44 
i  .  973  and  /3=66°  5'  The  characteristic  prismatic  faces  are 
(w)ooP(uo)  and  (J)ooP2(2io)  These  with  (b)  oo  P  5b  (oio)  con- 
stitute the  prismatic  zone  The  terminations  are  (r)  \?  00(012)  or 
(q)  Pob  (on)  in  combination  with  the  basal  plane  (0  oP(ooi),  the 
orthodome  (a)  (Toi),  and  one  or  more  of  several  pyramids  (See  Fig 
27 )  The  crystals  are  usually  small  and  are 
striated  vertically  Prismatic  angle  1 10  A  ilo 

=  105°  34' 

The  mineral  possesses  a  distinct  cleavage 
parallel  to  (fc)ooPoo  and  (/)  oo  P5  It  is 
sectile,  soft  (H=  i  5-2),  resinous  in  luster  and 
aurora-red  or  orange  in  color  Its  streak  is  a 
lighter  shade,  but  with  the  mineral  are  fre- 
quently intermingled  small  quantities  of  orpi- 
FIG  27  — Realgar  Crystal  ment  which  impart  to  its  streak  a  distinct 
yellow  tinge  Its  density  is  3  56  In  thin 
splinters  it  is  often  translucent  or  trans- 
parent, and  strongly  pleochroic  m  red  and 
yellow  tints,  but  in  masses  it  is  opaque  Its 
indices  of  refraction  are  not  known  with  accuracy,  but  its  double  re- 
fraction is  strong  ( 030)  It  is  a  nonconductor  of  electricity 

When  heated  on  charcoal  before  the  blowpipe  realgar  catches  fire 
and  burns  with  a  light  blue  flame,  at  the  same  time  giving  off  dense 
clouds  of  arsenic  fumes  and  the  odor  of  burning  sulphur  (SOs)  When 
heated  in  a  closed  tube  it  melts,  volatilizes  and  yields  a  transparent 
red  sublimate  in  the  cold  parts  of  the  tube 

Its  bright  red  color  and  its  reaction  for  sulphur  distinguish  realgar 
from  all  other  minerals  but  cinnalar,  the  sulphide  of  mercury  (p   9#) 
It  may  easily  be  distinguished  from  cinnabar  by  its  softness,  its  low 
specific  gravity  and  the  arsenic  fumes  which  it  yields  when  heated  on 

On  exposure  to  the  air  and  to  light  realgar  oxidizes,  yielding  orpi- 
ment  (As2Ss)  and  arsenolite  (As20s) 

Syntheses  —Realgar  is  often  produced  in  the  flues  of  furnaces  m 
which  ores  containing  sulphur  and  arsenic  are  roasted  Crystals  have 
also  been  produced  by  heating  to  150°  a  mixture  of  AsS  with  an  excess 
of  sulphur  in  a  solution  of  bicarbonate  of  soda  sealed  m  a  glass  tube 

Occurrence  Localities  and  Origin — Realgar  occurs  in  masses  asso 
dated  with  orpiment  and  m  grams  scattered  through  it  at  all  places 


where  the  latter  mineral  is  found  It  also  occurs  associated  with  silver 
and  lead  ores  in  many  places  It  is  found  in  crystals  implanted  on 
quartz  and  on  the  walls  of  cavities  in  lavas  It  "is  also  occasionally 
a  deposit  from  hot  springs  In  the  United  States  it  forms  seams  in  a 
sandy  clay  in  Iron  Co  ,  Utah  Its  crystals  are  found  in  calcite  in  San 
Bernardino  and  Trinity  Counties,  California,  and  with  orpiment  it  is 
deposited  as  a  powder  by  the  hot  water  of  the  Norns  Geyser  basin  in  the 
Yellowstone  National  Park 

In  most  cases  it  is  a  product  of  the  interaction  of  arsenic  and  sul- 
phur vapors. 

Uses  — The  native  realgar  occurs  in  too  small  a  quantity  to  be  of 
commercial  importance  An  artificial  realgar  is  employed  in  tanning 
and  m  the  manufacture  of  "  white-fire  " 

Orpiment  (As2S3) 

Orpiment,  though  more  abundant  than  realgar,  is  not  a  common 
mineral  It  is  usually  found  m  foliated  or  columnar  masses  with  a. 
bright  yellow  color  Its  name — a  contraction  from  the  Latin  aun- 
pigmentum,  meaning  golden  paint — refers  to  this  color 

The  pure  mineral  contains  39  per  cent  of  sulphur  and  61  per  cent 
of  arsenic,  corresponding  to  the  formula  As2Sa  It  thus  contains 
about  9  per  cent  more  sulphur  than  does  realgar. 

The  monoclmic  orpiment  crystals  have  the  symmetry  of  the  pris- 
matic class  Their  axial  ratio  is  596  .  i  *  665  with £=89°  19'  Though 
always  small  they  are  distinctly  prismatic  with  an  orthorhombic  habit 
Their  predominant  faces  are  the  ortho  and  clino  pmacoids,  several 
prisms  and  the  orthodome 

The  cleavage  of  orpiment  is  so  perfect  parallel  to  °o  P  ob  (oio)  that 
even  from  large  masses  of  the  mineral  distinct  foliae  may  be  split 
These  are  flexible  but  not  elastic  The  mineral,  like  many  other 
flexible  minerals,  is  sectile  Its  luster  is  pearly  on  cleavage  faces, 
which  are  always  vertically  striated,  and  is  resinous  on  other  surfaces 
The  color  of  pure  orpiment  is  lemon-yellow,  it  shades  into  orange 
when  the  mineral  is  impure  through  the  admixture  of  realgar  Its 
streak  is  always  of  some  lighter  shade  than  that  of  the  mineral  Its 
hardness  is  i  5-2  and  its  density  about  34  In  small  pieces  orpiment 
is  translucent  and  possesses  an  orange  and  greenish  yellow  pleochroism 
When  heated  to  100°  it  becomes  red  and  assumes  the  pleochroism  of 
realgar.  It,  however,  resumes  its  characteristic  color  and  pleochroism 
upon  cooling.  When  heated  to  150°  the  change  is  permanent.  The 
mineral  is  a  nonconductor  of  electricity. 


The  chemical  properties  of  orpiment  are  the  same  as  those  described 
for  realgar,  except  that  the  sublimate  in  the  closed  tube  is  yellow  instead 
of  red 

Synthesis  —Orpiment  is  produced  in  large  plcochroic  crystals  by 
treatment  of  arsenic  acid  with  H2S  under  high  prcssuie 

Occurrence,  Localities  and  Origin  —Orpiment  occurs  in  the  same 
forms  and  in  the  same  places  as  does  realgar  Small  specks  of  it  occur 
on  arsenical  iron  at  Edenville,  NY  It  is  also  found  in  the  deposits 
of  Steamboat  Springs  Nevada  The  origin  of  orpiment  is  similar 
to  that  of  realgar  It  is  also  formed  by  the  oxidation  of  this  mineral 

Uses  —Native  orpiment  mixed  with  water  and  slaked  lime  is  used 
in  the  East  as  a  wash  for  removing  hair  It  is  also  employed  as  a  pig- 
ment in  dyeing  Most  of  the  As2§3  of  commerce  is  a  manufactured 


The  stibmte  group  of  sulphides  contains  several  isomorphous 
compounds,  of  which  we  shall  consider  only  two,  viz  ,  Uibmtc 
and  Usmuthimte  (61283)  The  general  formula  of  the  group  is 
m  which  R  stands  for  Sb  or  Bi  and  Q  for  S  01  Se  The  gioup  is 
orthorhombic  (bipyramidal  class)  All  the  members  have  a  distinct 
cleavage  parallel  to  the  brachypmacoid  which  yields  flexible  laminae 

Sfobnite  (Sb2Sa) 

Stibmte  is  the  commonest  and  the  most  important  ore  of  anti- 
mony It  is  found  in  acicular  and  prismatic  crys- 
tals, in  radiating  groups  of  crystals  and  m 
fibrous  masses 

Chemically,  stibmte  is  the  antimony  tnsul- 
phide,  SboSa,  composed  of  SI),  71  4  per  cent 
and  S,  28  6  per  cent  Ab  found,  however,  it 
usually  contains  small  quantities  of  iron  and  often 
traces  of  silver  and  gold 

„       „    „  ,       ^  Crystals  of   stibmte  are  often  very  comnh- 

FIG    28  —Stibmte  Crys-        ,    ,     «,,  11,  i  . 

tal      M  p    no  (w)    ca^ec^    They  are  orthorhombic  with  an  axial  ratio 

OOP  So,  oio  (ft),  2P2^    9926  *  i    10179  and  a  columnar  or   acicular 
121  00  and  P,  iii(.p)     habit     The  most  important  forms  m  the  pris- 
matic zone  are  oo  P(no)  and  oo  P  56  (oio).    The 
prisms  are  often  acutely  terminated  by  P(iu),  ^4(431)  and  6P2»(36i), 
or  bluntly  terminated  by  iP(ii3),  (Fig    28)     Sometimes  the  crystals 
are  rendered  very  complicated  by  the  great  number  of  their  terminal 


planes     Dana  figures  a  crystal  from  Japan  that  possesses  a  termina- 
tion of  84  planes     no  A  ilo=89°  34' 

Many  of  the  crystals  of  this  mineral,  more  particularly  those  with 
an  acicular  habit,  are  curved,  bent  or  twisted  Nearly  "all,  whether 
curved  or  straight,  are  longitudinally  striated 

The  cleavage  of  stibmte  is  very  perfect  parallel  to  oo  P  06  (oio), 
leaving  striated  surfaces  The  mineral  is  soft  (H=2)  and  slightly 
sectile  Its  density  is  about  4  5  Its  color  is  lead-gray  and  its  streak 
a  little  darker  In  very  thin  splinters  it  is  translucent  in  red  or  yellow 
tints  In  these  the  indices  of  refraction  for  yellow  light  have  been 
determined  to  be,  0^=4303  and  7=3  194  Surfaces  that  are  exposed 
to  the  air  are  often  coated  with  a  black  or  an  iridescent  tarnish  The 
luster  of  the  mineral  is  metallic  It  is  a  nonconductor  of  electricity 

Stibmte  fuses  very  easily,  thin  splinters  being  melted  even  in  the 
flame  of  a  candle  When  heated  on  charcoal  the  mineral  yields  anti- 
mony and  sulphurous  fumes,  the  former  of  which  coat  the  charcoal  white 
in  the  vicinity  of  the  assay  When  heated  in  the  open  tube  SCb  is 
evolved  and  a  white  sublimate  of  Sb20s  is  deposited  on  the  cool  walls  of 
the  tube  In  the  closed  tube  the  mineral  gives  a  faint  ring  of  sulphur 
and  a  red  coating  of  antimony  oxysulphide  It  is  soluble  in  nitric  acid 
with  the  precipitation  of  Sb20s 

Stibmte  may  easily  be  distinguished  from  all  minerals  but  the  other 
sulphides  by  the  test  for  sulphur  From  the  other  sulphides  it  is  dis- 
tinguished by  its  cleavage  and  the  fumes  it  yields  when  heated  on  char- 
coal Its  closest  resemblance  is  with  galena  (PbS),  which,  however, 
differs  from  it  in  being  less  fusible  and  in  yielding  a  lead  globule  when 
fused  with  sodium  carbonate  on  charcoal.  Moreover,  galena  possesses 
a  cubic  cleavage 

Syntheses — Stibnite  is  produced  by  heating  to  200°,  a  mixture  of 
sulphur  and  antimony  with  water  under  pressure,  and  by  the  reaction  of 
H2S  on  antimony  oxide  heated  to  redness 

Occurrence,  Localities  and  Origin  — The  mineral  is  found  as  crystals 
in  quartz  veins  cutting  crystalline  rocks,  and  in  metalliferous  veins  asso- 
ciated with  lead  and  zinc  ores,  with  cinnabar  (HgS)  and  barite  (BaSO-i) 
The  finest  crystals,  some  of  them  20  inches  in  length,  come  from  mines 
in  the  Province  of  lyo,  on  the  Island  of  Shikoku/Japan  The  mineral 
occurs  also  m  York  Co ,  New  Brunswick,  in  Rawdon  township,  Nova 
Scotia,  at  many  points  in  the  eastern  United  States,  in  Sevier  Co  , 
Arkansas,  in  Garfield  Co  ,  Utah,  and  at  many  of  the  mining  districts  in 
the  Rocky  Mountain  States 

In  Arkansas  stibmte  is  in  quartz  veins  following  the  bedding  planes 


of  shales  and  sandstones  With  it  are  found  many  lead,  zmc  and 
iron  compounds  and  small  quantities  of  rarer  substances  In  Utah 
the  mineral  occurs  m  veins  unmixed  AMth  other  minerals,  except  its 
o\\n  oxidation  products  The  veins  follow  the  bedding  of  sandstones 
and  conglomerates  Here,  as  in  Arkansas,  the  stibnite  is  believed  to 
have  been  deposited  by  magmatic  waters 

Uses  —Stibnite  was  powdered  by  the  ancients  and  used  to  color  the 
eyebrows,  eyelashes  and  hair  At  present  it  is  used  to  a  slight  extent  in 
vulcanizing  rubber  and  in  the  manufacture  of  safety  matches,  percussion 
caps,  certain  kinds  of  fireworks,  etc  Its  principal  value  is  as  an  ore  of 
antimony  Practically  all  of  the  metal  used  in  the  arts  is  obtained 
from  this  source  Antimony  is  chiefly  valuable  as  an  alloy  with  other 
metals  With  tin  and  lead  it  forms  type  metal  The  principal  alloys 
with  tin  are  britannia  metal  and  pewter  With  lead,  tin  and  copper 
it  constitutes  babbit  metal,  a  hard  alloy  used  in  the  construction  of 
locomotive  and  car  journals,  and  with  other  substances  it  enters  into 
the  composition  of  other  alloys  used  for  a  variety  of  purposes  The 
double  tartrate  of  antimony  and  potassium  is  the  well  known  tartar 
emetic.  The  pigment,  Naples  yellow,  is  an  antimony  chromate. 

Production  — The  total  quantity  of  stibnite  mined  in  the  world  can- 
not be  accurately  estimated  That  mined  in  the  United  States  is  very 
small  in  amount,  most  of  the  antimony  produced  m  this  country  being 
obtained  in  the  form  of  an  antimony  alloy  as  a  by-product  in  the  smelting 
of  antunomal  lead  ores 

Bismuthinite  (Bi2S3) 

Bismuthimte  is  completely  isomorphous  with  stibnite  It  rarely, 
however,  occurs  in  acicular  crystals,  but  is  more  frequently  in  foliated, 
fibrous  or  dense  masses 

Its  axial  ratio  is  968    i  :  985. 

The  angle  noAiTo  =  88°  8' 

The  mineral  resembles  stibnite  in  color  and  streak,  but  its  surface  is 
often  covered  with  a  yellowish  iridescent  tarnish  Its  fusibility  and 
hardness  are  the  same  as  those  of  stibnite  but  its  density  is  6  8-7  i  It 
is  an  electrical  conductor 

In  the  open  tube  the  mineral  yields  S02  and  a  white  sublimate 
which  melts  into  drops  that  are  brown  while  hot,  but  change  to  opaque 
yellow  when  cold  On  charcoal  it  yields  a  coating  of  yellow  81203  which 
changes  to  a  bright  red  Bils  when  moistened  with  potassium  iodide 
The  mineral  dissolves  in  hot  nitric  acid,  forming  a  solution,  which  upon 
the  addition  of  water  gives  a  white  precipitate  of  a  basic  bismuth  nitrate. 


Bismuthmite  is  distinguished  from  stibmte  by  the  coating  on  char- 
coal and  by  its  complete  solubility  in  HNOa 

Syntheses  — Crystals  have  been  obtained  by  cooling  a  solution  of 
m  molten  bismuth,  and  by  cooling  a  solu.ion  made  by  heating 
BioSs  m  a  solution  of  potassium  sulphide  in  a  closed  tube  at  200°. 

Occurrence ,  Localities  and  Origin  — Bismuthmite  occurs  as  a  constit- 
uent of  veins  associated  \vith  quartz,  bismuth  and  chalcopynte,  in  which 
it  was  probably  formed  as  a  product  of  pneumatolytic  processes  It  is 
found  at  Schneeberg  and  other  points  in  Saxony,  at  Redruth  and 
elsewhere  in  Cornwall,  near  Beaver  City,  Utah,  in  a  gold-bearing  veiii 
at  Gold  Hill,  Rowan  County,  N  C  ,  and  in  a  vein  containing  benl, 
garnet,  etc ,  in  granite  at  Haddam,  Conn 


This  group  comprises  a  series  of  tellundes  and  selemdes  of  bismuth 
that  have  not  been  satisfactorily  differentiated  because  of  the  lack  of 
accurate  analyses 

Tetradymite,  the  best  known  member  of  the  group,  is  probably  an 
isomorphous  mixture  cf  bismuth  tellunde  and  bismuth  sulphide  of  the 
formula  Bi2(Te  8)3  It  occurs  in  small  rhombohedral  cnstals  with  the 
axial  ratio  i  .  i  587  and  loli  A  1101  =  98°  58'  Its  crystals  are  bounded 
by  rhombohedrons  (R(ioTi)  and  2R(202ii))  and  the  basal  plane 
(oP(oooi)).  Interpenetration  fourlings  are  common  with  — |R(oil2), 
the  twinning  plane  The  mineral  is,  however,  more  frequently  found 
in  foliated  and  granular  masses.  Its  color  is  lead-gray  It  possesses  a 
perfect  cleavage  parallel  to  the  base  Its  hardness  is  i  5-2  and  its 
density  about  74  It  is  a  good  electncal  conductor  Its  best  known 
occurrences  are  Zsubkau,  Hungary,  Whitehall,  Va,  in  Davidson 
County,  N  C ,  near  Dahlonega,  Ga ,  near  Highland,  Mont ,  and  at 
the  Montgomery  Mine  and  at  Bradshaw  City  in  Arizona  It  occurs  in 
quartz  veins  associated  with  gold  in  the  gold  sands  of  some  streams 

The  other  members  of  the  group  appear  to  be  completely  isomorphous 
with  tetradymite.  They  vary  m  color  from  tin-white  through  gray  to 

Molybdenite  (MoS) 

This  mineral,  which  is  the  sulphide  of  the  rare  metal  molybdenum, 
does  not  occur  in  large  quantity,  but  it  is  so  widely  distributed  that  it 
seems  to  be  quite  abundant  It  occurs  principally  in  black  scales  scat- 


tered  through  coarse-grained,  crystalline,  siliceous  rocks  and  granular 
limestones  and  in  black  or  lead-gray  foliated  masses 

The  theoretical  composition  of  molybdenite  is  40  per  cent  sulphur 
and  60  per  cent  molybdenum  Usually,  however,  the  mineral  contains 
small  quantities  of  iron  and  occasionally  other  components 

Crystals  of  molybdenite  are  exceedingly  rare  Scales  and  plates 
with  hexagonal  outlines  are  often  met  with  but  they  do  not  usually  pos- 
sess sufficiently  perfect  faces  to  >ield  accurate  measurements  The 
measurements  that  have  been  obtained  appear  to  indicate  a  holohedral 
hexagonal  symmetry  with  an  axial  ratio  i  i  908 

The  cleavage  of  molybdenite  is  very  perfect  parallel  to  the  base. 
The  laminae  are  flexible  but  not  elastic  The  mineral  is  sectile  and  so 
soft  that  it  leaves  a  black  mark  when  drawn  across  paper  Its  density 
is  4  7.  Its  luster  is  metallic,  color  lead-black,  and  streak  greenish 
black  In  very  thm  flakes  the  mineral  is  translucent  with  a  green  tinge 
Otherwise  it  is  opaque  It  is  a  poor  conductor  of  electricity  at  ordi- 
nary temperature,  but  its  conductivity  increases  with  the  temperature 

In  the  blowpipe  flame  molybdenite  is  infusible  It,  however,  im- 
parts to  the  edges  of  the  flame  a  yellowish  green  color  Naturally,  it 
yields  all  the  reactions  for  sulphur,  and  in  the  open  tube  it  deposits  a 
pale  yellow  crystalline  sublimate  of  MoOs  Molybdenite  is  decomposed 
by  nitric  acid  with  the  production  of  a  gray  powder  (MoOs) 

By  its  color,  luster  and  softness  molybdenite  is  easily  distinguished 
from  all  minerals  but  graphite  From  this  it  is  distinguished  by  its 
reaction  for  sulphur  Moreover,  a  characteristic  test  foi  all  molyb- 
denum compounds  is  the  dark  blue  coating  produced  on  porcelain  when 
the  pulverized  substance  is  moistened  with  concentrated  sulphuric 
acid  and  then  heated  until  almost  dry  Before  this  test  can  be  applied 
to  molybdenite,  the  mineral  must  first  be  powdered  and  then  oxi- 
dized by  roasting  in  the  air  for  a  few  minutes  or  by  boiling  to  dryness 
with  a  few  drops  of  HNOs 

Syntheses  —Crystalline  molybdenite  has  been  prepared  by  the  action 
of  sulphur  vapor  or  EfeS  upon  glowing  molybdic  acid  It  has  also  been 
produced  by  heating  a  mixture  of  molybdates  and  lime,  in  a  large  excess 
of  a  gaseous  mixture  of  HC1  and  EfeS. 

Occurrence,  Localities  arid  Origin — Molybdenite  generally  occurs 
^embedded  as  grams  in  limestone  and  in  the  crystalline  silicate  rocks, 
as,  for  instance,  granite  and  gneiss,  and  as  masses  in  quartz  veins,  at 
Arendal,  Norway,  at  Blue  Hill  Bay,  Maine,  at  Haddam,  Conn  ,  m 
Renfrew  Co ,  Ontario,  and  at  many  points  in  the  far  western  states 
It  is  thought  to  be  of  pneumatolytic  origin. 


Uses  — The  mineral  is  the  principal  ore  of  the  metal  molybdenum, 
the  salts  of  which  are  important  chemicals  employed  principally  in 
analytical  work,  especially  in  the  detection  and  estimation  of  phosphoric 
acid  The  mol^bdate  of  ammonia  (NH^MoO^  the  principal  salt 
employed  in  analytical  processes,  is  easily  obtained  by  roasting  a  mix- 
ture of  sand  and  molybdenite  and  treating  the  oxidized  product  with 
ammonia  Other  molybdenum  salts  are  used  for  giving  a  green  color 
to  porcelain  The  metal  is  used  in  an  alloy  (ferro-mol}bdenum)  for 
hardening  steel,  as  supports  for  the  lower  ends  of  tungsten  filaments  in 
electric  lamps  and  for  making  ribbons  used  in  electric  furnaces 

Production — There  was  no  production  of  molybdenite  in  North 
America  during  1912  The  imports  of  the  metal  into  the  United  States 
aggregated  3  5  tons,  valued  at  $4,670.  The  value  of  the  imports 
of  the  ore  is  not  known* 


The  metallic  monosulphides,  monoselemdes,  etc ,  are  compounds 
in  which  the  hydrogen  of  H2S,  H2Se,  H2Te,  HsAs,  and  HsSb  are 
replaced  by  metals  Among  them  are  some  of  the  most  important 

They  may  be  separated  into  several  groups  of  which  some  are 
among  the  best  defined  of  all  the  mineral  groups,  while  others  consist 
simply  of  a  number  of  minerals  placed  together  solely  for  convenience 
of  description  In  addition,  there  are  a  few  members  of  this  chemical 
group  which  seem  to  have  no  close  relationship  with  any  other  mem- 
bers These  are  discussed  separately 

The  groups  described  are  as  follows: 

The  Dyskrasite  Group 
The  Galena  Group 
The  Chalcocite  Group. 
The  Blende  Group 
The  Millerite  Group 
The  Cinnabar  Group. 


This  group  includes  a  number  of  arsenides  and  antimonides,  some 
of  which  apparently  contain  an  excess  of  the  metal  above  that  neces- 
sary to  satisfy  the  formulas  HsAs  and  HsSb.  Although  their  com- 


position  is  not  understood,  they  are  generally  regarded  as  basic  com- 
pounds A  few  of  them  are  well  crystallized,  but  their  composition  is 
doubtful,  because  of  the  difficulty  of  obtaining  pure  material  for  anal- 
yses Some  of  them  are  probably  mixtures  The  members  of  the 
group,  all  of  which  are  ccmparatrvely  rare,  are  wkitneyite  (CuoAs), 
algodomte  (CueAs),  domeykite  (CuaAs),  horsfordite  (Cu^Sb)  and  dyskras- 
ite (AgaSb)  Other  minerals  are  known  which  may  properly  be  placed 
here,  but  their  identity  is  doubtful  The  only  two  members  that  need 
further  discussion  are  domeykite  and  dyskrasite 

Domeykite  (CuaAs)  is  known  only  in  disseminated  particles  and 
in  botryoidal  and  dense  masses  and  small  orthorhombic  crystals  It 
may  be  a  mixture  of  several  components,  which  in  other  proportions 
form  algodomte  It  is  tin-white  or  steel-gray  and  opaque  It  becomes 
dull  and  covered  with  a  yellow  or  brown  iridescent  tarnish  when  ex- 
posed to  the  air  Its  hardness  is  3-4  and  density  about  73  It  is  the 
most  easily  fusible  of  the  copper  arsenides  Its  principal  occurrences 
are  m  the  silver  mines  of  Copiapo  and  Coquimbo  in  Chile,  associated 
T\ith  native  copper  at  Cerro  de  Paracabas,  Guerrero,  Mexico,  at  Shel- 
don, Portage  Lake,  Michigan,  and  on  Michipicoten  Island,  in  Lake 
Superior,  Ontario  The  last  two  occurrences  are  in  quartz  veins 

Dyskrasite  (AgaSb)  occurs  in  foliated,  granular  and  structureless 
masses  and  rarely  in  small  orthorhombic  crystals  with  an  hexagonal 
habit     Their  axial  ratio  is    5775    i  .  6718,    Twinning  is  frequent, 
yielding  star-shaped  aggregates     The  mineral  has  a  silver-white  color 
and  streak,  but  its  exposed  surfaces  are  often  tarnished  yellow  or  bUck 
It  is  opaque  and  sectile     Its  hardness  is  3  5-4  and  density  about  9  6 
It  is  a  good  electrical  conductor     Dyskrasite  is  soluble    in    HNO^ 
leaving  a  white  sediment  of  Sb20s     It  occurs  principally  in  the  silver 
mines  of  central  Europe,  and  especially  near  Wolfach,  Baden,    St 
Andreasberg,  Harz,  and  at  Carnzo,  in  Copiapo,  Chile. 


The  minerals  comprising  the  galena  group  number  about  a  dozen 
crystallizing  m  the  holohedral  division  of  the  regular  system  (hex- 
octahedral  class)  They  possess  the  general  formula  RQ  in  which 
R  represents  silver,  lead,  copper  and  gold,  and  Q  sulphur,  selenium 
and  tellurium  The  group  may  be  divided  into  silver  compounds  and 
lead  compounds,  thus  (A)  argentite  (Ag2S),  hessite  (Ag2Te),  petzite 
((Ag  Au)2Te),  naumanmte  (Ag2Se),  agmlante  (Ag2(Se  S)),  jalpaitc 


((Ag  Cu)2S)  and  eukante  ((Ag  Cu)2Se),  and  (B)  galena  (PbS\  altaite 
(PbTe),  and  dausttalite  (PbSe)  Of  these  onh  two  are  of  importance, 
viz,  galena,  and  argentite  Hessite  and  petzite  are  comparative!} 
unimportant  ores  of  gold 

Argentite  (AgoS) 

Argentite,  though  not  very  widespread  m  its  occurrence,  is  an 
important  ore  of  silver  It  is  found  in  masses,  as  coatings,  and  in  crys- 
tals or  arborescent  groups  of  crystals 

Argentite  contains  87  i  per  cent  silver  and  12  9  per  cent  sulphur  when 
pure  It  is  usually,  however,  impure  through  the  admixture  of  small 
quantities  of  Fe,  Pb,  Cu,  etc 

The  forms  most  frequently  observed  on  argentite  crystals  are 
ooOoo(ioo),  ooO(no)  and  0(in),  though  various  wOoo  (hid)  and 
wOm  (hll)  forms  are  also  met  Tvith  The  crystals  are  often  distorted 
and  often  they  are  grouped  in  paiallel  growths  of  different  shapes 
Twinning  is  common,  with  0(in)  the  twinning  plane  The  twins 
are  usually  penetration  twins  The  habit  of  most  crystals  is  cubical 
or  octahedral 

Argentite  is  lead-gray  in  color  Its  streak  is  a  little  darker  The 
mineral  is  opaque  Its  luster  is  metallic,  its  hardness  about  2  25  and* 
density  73  It  is  sectile,  has  an  imperfect  cleavage  and  is  a  conductor 
of  electricity 

When  heated  on  charcoal  argentite  shells  and  fuses,  yielding  sulphur 
fumes  and  a  globule  of  silver  It  is  soluble  m  nitric  acid 

Argentite  is  easily  recognized  by  its  color,  its  sectility,  the  fact  that 
it  yields  a  silver  globule  when  fused  with  Na2COs  on  charcoal  and  yields 
the  sulphur  test  with  a  silver  corn 

Syntheses  — Crystals  of  argentite  may  be  obtained  by  treating  red 
hot  silver  with  sulphur  vapor  or  dry  HfcS,  and  by  heating  silver  and  SCb 
in  a  closed  tube  at  200° 

Occurrence,  Localities  and  Origin  — The  mineral  is  found  in  the  second- 
ary enrichment  zones  of  veins  associated  with  silver  and  other  sulphides 
in  many  silver-mining  districts  In  Nevada  it  is  an  important  ore  at 
the  Comstock  lode  and  in  the  Cortez  district  It  is  found  also  near 
Port  Arthur  on  the  north  shore  of  Lake  Superior,  in  Ontario,  and  asso- 
ciated with  native  silver  in  the  copper  mines  of  Michigan  The  ores  of 
Mexico,  Chile,  Bolivia  and  Peru  are  composed  largely  of  this  mineral. 

Production  — Much  of  the  silver  produced  in  this  country  is  obtained 
from  argentite,  though  by  no  means  so  great  a  quantity  as  is  obtained 
from  other  sources* 


Hessite  (Ag2Te)  and  Petzite  ((Ag  Au)2Te) 

These  two  minerals,  though  comparatively  rare,  are  prominent 
sources  of  gold  and  silver  in  some  mining  camps  They  usually  occur 
together  associated  with  other  sulphides. 

Hessite  is  the  nearly  pure  silver  tellunde  and  petzittf,  &n  isomorphous 
mixture  of  gold  and  silver  tellundes,  as  indicated  by  the  following  analy- 
ses of  materials  from  the  Red  Cloud  Mine,  Boulder  Co  ,  Colorado 



Au         Cu 

Pb      Fe 






59  9i 

22           17 

45    i  35 

99  96 


34  9i 

50  66 

13  09       °7 

17        36 



100   01 


32  97 

40  80 

24  69 

i  28 



100   00 

The  minerals  crystallize  in  all  respects  like  argentite  They  are 
opaque  and  lead-gray  to  iron-black  in  color,  sectile  to  brittle,  have  a 
hardness  between  2  and  3  and  a  specific  gravity  of  8  3-9,  increasing  with 
the  percentage  of  gold  present  They  are  good  conductors  of  electricity 

Before  the  blowpipe,  both  minerals  melt  easily  to  a  black  globule,  at 
the  same  time  coloring  the  reducing  flame  greenish  and  giving  the  odor 
of  tellurium  fumes  When  acted  upon  by  the  reducing  flame,  the  globule 
becomes  covered  with  little  crystals  of  silver  With  Na2COs  on  charcoal 
both  minerals  yield  a  globule  of  silver,  but  the  globule  obtained  from 
hessite  dissolves  in  warm  HNOs,  while  that  obtained  from  petzite 
becomes  yellow  (gold)  In  the  open  tube  both  yield  a  white  sublimate 
of  TeO2  which  melts,  when  heated,  to  colorless  drops  When  heated 
with  concentrated  H^SCU,  they  give  a  purple  or  red  solution  which,  upon 
the  addition  of  water,  loses  its  color  and  precipitates  blackish  gray, 
powdery  tellurium.  The  minerals  dissolve  in  HNOs  From  this  solu- 
tion HC1  throws  down  white  silver  chloride 

Both  the  minerals  resemble  very  closely  many  forms  of  argentite 
and  galena,  from  which,  however,  they  may  be  distinguished  by  the 
reactions  for  tellurium  Petzite  and  hessite  may  be  distinguished  from 
one  another  by  the  test  for  gold  Moreover  a  fresh  surface  of  hessite 
blackens  when  treated  with  a  solution  of  KCN,  whereas  a  surface  of 
petzite  remains  unaffected 

Syntheses  —Octahedrons  of  hessite  are  obtained  by  the  action  of 
tellurium  vapor  upon  glowing  silver  in  an  atmosphere  of  nitrogen,  and 
dodecahedrons  of  petzite  upon  similar  treatment  of  gold-silver  alloy 

Origin — Both  minerals  are  believed  to  be  primary  deposits  orig- 
inating in  magmatic  solutions  They  occur  in  veins  with  native  gold, 
quartz,  fluonte,  dolomite,  and  various  sulphides  and  other  tellundes. 


Localities  —These  tellundes,  together  uith  others  to  be  described 
later  (p  113),  are  important  sources  of  silver  and  gold  in  the  mines  at 
Nagyag,  Transylvania,  at  Cripple  Creek  and  in  Boulder  Co  ,  Colo  ,  and 
at  Kalgoorhe,  W  Australia  The  quantity  of  tellundes  mined  is  con- 
siderable, but  since  it  is  impracticable  to  separate  these  t\\o  tellundes 
from  the  other  compounds  of  gold  and  silver  mined  with  them,  it  is  im- 
possible to  estimate  the  proportion  of  the  metals  obtained  from  them 

Galena  (PbS) 

Galena,  the  most  important  ore  of  lead,  occurs  in  great  lead-gray 
crystalline  masses,  in  large  and  small  crystals,  in  coarse  and  fine  granukr 
aggregates,  and  in  other  less  common  forms  Much  galena  contains 
silver,  m  which  case  it  becomes  an  important  ore  of  this  metal 

Galena  rarely  approaches  the  theoretical  composition  13  4  per  cent 
cf  sulphur  and  86  6  per  cent  of  lead  It  usually  contains  small  quanti- 
ties of  the  sulphides  cf  silver,  zinc,  cadmium,  copper  and  bismuth  and 
in  some  cases  native  silver  and  gold  When  the  percentage  of  silver 
present  reaches  3  oz  per  ton  the  mineral  is  ranked  as  a  silver  ore  This 
silver  is  apparently  present  in  some  cases  as  an  isomorphous  mixture 
of  silver  sulphide  and  m  other  cases  in  distinct 
minerals  included  within  the  galena 

Galena  crystals  usually  possess  a  cubical  habit, 
though  crystals  with  the  octahedral  habit  are 
very  common  The  principal  forms  observed  are 

ooOoo(ioo),  0(in),    ooO(no),  mQoo(klo)  and  

mQm  (hlT)  (Figs   29  and  30)     Twins  are  common, 
\\ith  0  the  twinning  face  FlG  29  -Galena  ays- 

Galena  is  well  characterized  by  its  lead-gray      *        *    °°'    J,°? 
color,  its  perfect  cleavage  parallel  to  the  cubic  faces     an^  Q,  ni  (o) 
and  by  its  great  density  (8  5)     Its  luster  is  me- 
tallic and  its  hardness  about  2  6     Its  streak  is  grayish  black.    It  is  a 
good  conductor  of  electricity 

On  charcoal  galena  fuses,  yielding  sulphurous  fumes  and  a  globule 
of  metallic  lead,  which  may  easily  be  distinguished  from  a  silver  globule 
by  its  softness  The  charcoal  around  the  assay  is  coated  with  a  yellow 
sublimate  of  lead  oxide  (PbO)  The  mineral  is  soluble  in  HNOs  with 
the  separation  of  sulphur 

Its  color  and  luster  distinguish  galena  from  nearly  all  minerals  but 
s  Unite  From  this  mineral  it  is  easily  distinguished  by  its  more  difficult 
fusibility,  by  its  cleavage,  and  by  the  fact  that  it  does  not  yield  the  anti- 
mony fumes  when  heated  on  charcoal 



Galena  weathers  readily  to  the  sulphate  (anglesite)  and  carbonate 
(cerussite) ,  consequently  it  is  usually  not  found  m  the  upper  portions 
of  veins  that  are  exposed  to  the  action  of  the  air. 

Syntheses  —Crystals  of  galena  result  from  heating  a  mixture  of 
lead  oxide  with  NEUCl  and  sulphur,  and  from  treatment  of  a  lead  salt 
with  HgS  at  a  red  heat  Small  crystals  have  been  produced  by  heating 

FIG  30 — Galena  Crystals  (<*>OQ°(IOO)  and  O(in))  partly  covered  by  Manasitc, 
from  the  Joplm  District,  Mo     (After  UT  6   T  Smith  and  C  I1  bitbentlial ) 

in  a  sealed  glass  tube  at  8o°-9o°  pulverized  cerussite  (PbCO,j)  in  a  water 
solution  of  HkS 

Origin  — Veins  of  galena  containing  silver  (silver-lead)  were  probably 
produced  by  ascending  solutions  emanating  from  bodies  of  igneous 
rocks,  while  the  galena  in  limestone  was  probably  deposited  by  ground- 
water  that  dissolved  the  sulphide  from  the  surrounding  sedimentary 
rocks  Galena  is  also  in  some  cases  a  metamorphic  product 

Occurrence — The  mineral  occurs  very  widely  spread  It  is  found 
in  veins  associated  with  quartz  (SiCfe),  calcite  (CaCOa),  bante  (BaSOi) 
or  fluonte  (CaF2)  and  various  sulphides,  especially  the  zinc  sulphide, 
sphalerite,  in  irregular  masses  filling  clefts  and  cavities  in  limestone, 


in  beds,  and  in  stalactites    and   other  forms  characteristic  of  water 

It  occurs  also  as  pseudomorphs  after  pyromorphite— the  lead  phos- 
phate The  form  that  occurs  in  veins  is  often  silver  bearing,  while  that 
in  limestone  is  usually  free  from  silver 

Localities  — Galena  is  mined  m  Cornwall  and  in  Derbyshire,  Eng- 
land, in  the  Moresnet  district,  Belgium,  at  various  places  in  Silesia, 
Bohemia,  Spam  and  Australia  In  the  United  States  it  occurs  in  veins  at 
Lubec,  Me  ,  at  Rossie,  St  Lawrence  Co  ,  N  Y ,  at  PhoenL\ville,  Penn  ,  at 
Austin's  Mines  in  Wythe  Co  ,  Va  ,  and  at  many  other  places  It  is 
mined  for  silver  in  Mexico,  at  Leadville,  Colo  ,  at  various  points  in 
Montana,  in  the  Cceur  d'Alene  region  in  Idaho  and  at  many  other  places 
in  the  Rocky  Mountain  region 

The  most  extensive  galena  deposits  in  this  country  are  in  Missouri, 
m  the  corner  made  by  the  states  of  Wisconsin,  Illinois  and  Iowa,  and 
in  Cherokee  Co  ,  Kansas  In  these  districts  the  galena,  associated 
with  sphalerite  (ZnS),  pynte  (FeS2),  smithsomte  (ZnCOs),  calamine 
((ZnOH)2SiO3),  cerussite  (PbC03),  calcite  (CaCOa)  and  other  minerals, 
fills  cavities  in  limestone 

Extraction  of  Lead  and  Silver  from  Galena  — The  ore  is  first  crushed 
and  concentrated  by  mechanical  or  electrostatic  methods,  and  the 
concentrates  are  roasted  to  convert  them  into  oxides  and  sulphates 
The  mass  is  then  heated  without  access  of  air,  sulphur  dioxide  being 
driven  off,  leaving  metallic  lead  carrying  impurities,  or  a  mixture  of 
lead  and  silver 

The  processes  employed  in  refining  the  impure  lead  vary  with  the 
nature  of  the  impurities 

Uses — Galena  is  employed  to  some  extent  in  glazing  common 
stoneware  It  is  also  used  in  the  preparation  of  white  lead  and  other 
pigments  As  has  alrercly  been  stated,  it  is  the  most  important  ore  of 
lead  and  a  very  important  ore  of  silver 

The  metal  lead  finds  many  uses  in  the  arts  Its  most  common 
use  is  for  piping  Its  alloys,  type  metal,  pewter  and  babbitt  metal 
have  already  been  referred  to  (p  74)  Solder  is  an  alloy  of  tin  and  lead, 
Wood's  metal  a  mixture  of  lead,  bismuth,  tin  and  cadmium  The  spe- 
cial characteristic  of  Wood's  alloy  is  its  low  fusion  point  (70°) 

Production  —The  total  production  of  galena  by  the  different  coun- 
tries of  the  world  cannot  be  given,  but  the  world's  production  of  lead 
in  1912  was  1,277,002  short  tons  The  total  quantity  of  lead  pro- 
duced by  the  United  States  from  domestic  ores  in  the  same  year  was 
about  415,395  tons,  valued  at  $37,385>55°  M°st  of  this  was  obtained 


from  galena  About  171,037  tons  were  soft  lead,  smelted  from  ores 
mined  mainly  for  their  lead  and  zinc  contents,  and  the  balance  from 
ores  mined  partly  for  their  silver  The  importance  of  galena  as  an  ore 
of  silver  may  be  appreciated  from  the  fact  that  of  the  $39,197,000 
worth  of  this  metal  produced  in  the  United  States  during  1912,  silver 
to  the  value  of  about  $12,000,000  was  obtained  from  lead  ores  or  from 
mixtures  of  lead  and  zinc  ores 

Altaite  (PbTe)  and  clausthalite  (PbSe)  both  resemble  galena  m 
appearance  Both  occur  commonly  in  fine-grained  masses,  but  they 
are  also  found  in  cubic  crystals  Altaite  is  tin-white,  tarnishing  to 
yellow  or  bronze,  and  clausthahte  is  lead-gray  Their  hardness  is  2  5-3 
and  specific  gravity  about  8  i  They  are  associated  with  silver  and  lead 
compounds  principally  in  the  silver  mines  of  Europe  and  South  America 
Altaite  is  known  also  from  several  mines  in  California,  Colorado  and 
North  Carolina  They  are  distinguished  from  one  another  and  from 
galena  by  the  tests  for  Te  and  Se 


The  chalcocite  group  includes  four  or  five  cuprous  and  argentous 
sulphides,  selemdes  and  tellundes  They  all  crystallize  in  the  ortho- 
rhombic  system  (rhombic  bipyramidal  class)  often  with  an  hexagonal 
habit,  and  are  isomorphous  The  best  known  members  of  the  group 
are  chalcoc^te  (Cu2S)  and  stromeyente  (Cu  AgJgS,  but  only  the  first- 
named  is  common  Although  these  minerals  are  orthorhombic,  never- 
theless Cu2S  is  known  to  exist  also  in  isometric  crystals,  in  which  form 
it  is  isomorphous  with  argentite  Moreover,  stromeyente  is  an  iso- 
morphous mixture  of  Ag2$  and  Cu2S  Therefore,  it  is  inferred  that 
and  AggS  are  isomorphous  dimorphs 

Chalcocite  (Cu2S) 

Chalcocite  (Cu2S),  the  cuprous  sulphide,  is  an  important  ore  of 
copper  though  by  no  means  as  widely  spread  as  the  iron-copper  sul- 
phide, chalcopyrite  It  is  usually  found  in  black  masses  with  a  dull 
metallic  luster  and  as  a  black  powder,  though  frequently  also  in  crys- 
tals It  is  a  common  constituent  of  the  enrichment  zone  of  many  veins 
of  copper  ores, 

The  best  analyses  of  chalcocite  agree  closely  with  the  formula 
given  above,  requiring  the  presence  of  20  2  per  cent  of  sulphur  and 
79  8  per  cent  of  copper  Iron  and  silver  are  often  present  in  the  mineral 
in  small  quantity 


In  crystallization  chalcocite  is  orthorhombic  (rhombic  bipyramidal 
class)  with  the  axial  ratio  5822  .  i  9701  Its  crystals  contain  as 
their  predominant  forms  oP(ooi),  ooP(no),  ooP  00(010),  P(in), 

a  series  of  prisms  of  the  general  symbol  -P(iiA).  and  several  bra- 


chydomes     Many  cf  the  crystals  are  elongated  parallel  to  #,  and 
others  are  so  developed  as  to  possess  an  hexagonal  habit  (Fig   31) 
Twins  are  common  according  to  several  laws    When  the  twinning  plane  is 
|P  (112)  the  twins  are  usually  cruciform  (Fig  32)     The  zone  ooi—  oio 
is  often  striated  through  oscillatory  combinations     iioAiib=6o°  25' 
The  cleavage  of  chalcocite  is  indistinct,  its  fracture  is  conchoidal 
Its  hardness  is  2  5-3  and  density  about  5  7.    Its  streak,  like  its  color, 

FIG  31  FIG  32 

FIG  31  — Chalcocite  Crystal     oP,  ooi  (c),    «  p  So ,  oio  (ft),    °o  P,  no  (m),  2?  £  , 

021  (d),   |P w,  023  (<0,  P,  iii  (p)  and  JP,  113  00 

FIG  32  — Complex  Chalcocite  Twin,  with  °o  P,  no  (m)  and  |P,  112  (p)  the  Twinning 


is  nearly  black,  but  exposed  surfaces  are  often  tarnished  blue  or  green, 
probably  through  the  production  of  thin  films  of  other  sulphides  like 
covellite  (CuS),  chalcopynte  (FeCuSa),  etc  The  mineral  is  an  excel- 
lent conductor  of  electricity 

In  the  open  tube  or  on  charcoal  chalcocite  melts  and  yields  sul- 
phurous fumes 

When  mixed  with  Na2COs  and  heated  a  copper  globule  is  produced. 
The  mineral  dissolves  in  nitric  acid  with  the  production  of  a  solution 
that  yields  the  test  for  copper. 

Upon  exposure  to  the  air  chalcocite  changes  readily  to  the  oxide, 
cupnte  (CusO),  and  the  carbonates,  malachite  and  azurite.  In  the 
presence  of  siliaous  solutions  it  may  give  rise  to  the  silicate,  chrysocolla 

(P  44i)  . 

A  pseudomorph  of  chalcocite  after  galena  is  known  as  Aomnfe. 


It  occurs  at  the  Canton  Mine  m  Georgia  and  in  the  Polk  Co  copper 
mines  in  Tennessee  Pseudomorphs  after  many  other  copper  min- 
erals are  common 

Chalcocite  is  recognized  by  its  color  and  crystallization  Massive 
varieties  are  distinguished  from  argentite  by  greater  bnttleness  and  the 
reaction  for  copper,  from  bormte  (CusFeSs)  by  the  fact  that  it  is  not 
magnetic  after  roasting 

Syntheses  — Crystals  of  chalcocite  have  been  made  in  many  ways, 
more  particularly  by  heating  the  vapors  of  CuCb  and  H^S,  and  by 
gently  warming  CuaO  in  B^S  Measurable  crystals  have  been  observed 
on  old  bronze  that  has  been  immersed  m  the  waters  of  hot  springs  for 
a  long  time 

Occurrence ,  Localities  and  Origin  —The  mineral  is  a  common  prod- 
uct of  the  alteration  of  other  copper  compounds  in  the  zone  of  secondary 
enrichment  of  sulphide  veins.  It  is  therefore  present  at  most  localities 
of  copper  minerals  One  of  the  best  known  occurrences  is  Butte, 

Fine  crystals  of  chalcocite  occur  in  veins  and  beds  at  Redruth  and 
at  other  places  m  Cornwall,  England,  at  Bristol  m  Connecticut,  and 
at  Joachunthal  in  Bohemia  The  massive  variety  is  known  at  many 
places  In  the  United  States  it  occurs  m  red  sandstone  at  Cheshire 
in  Connecticut  It  is  found  also  in  large  quantities  near  Butte  City  in 
Montana,  and  in  Washoe  and  other  counties  in  Nevada,  and  indeed 
in  the  veins  of  most  copper  producing  mines  In  Canada  it  is  present 
with  chalcopynte  and  bormte  at  Acton,  Quebec,  and  at  several  places 
in  Ontario  north  of  Lake  Superior 

Extraction  of  Copper — Chalcocite  rarely  occurs  alone  in  large 
quantity.  In  ores  it  is  usually  mixed  with  other  compounds  of  copper, 
and  is  treated  with  them  in  extracting  the  metal  (see  p.  133). 

Stromeyerite  ((Ag  Cu)2S)  is  usually  massive,  but  it  occurs  also  in 
simple  and  twinned  crystals  similar  to  those  of  chalcocite  Their  axial 
ratio  is  5822  i  :  9668,  almost  identical  with  that  of  chalcocite  The 
mineral  is  opaque  and  metallic  Its  color  and  streak  are  dark  steel- 
gray  Its  hardness  is  2  5-3  and  density  about  62  It  is  soluble  m 
nitric  acid  It  occurs  associated  with  other  sulphides  in  the  ores  of 
silver  and  copper  mines  at  Schlangenberg,  Altai,  Kupferberg,  Silesia, 
Coquimbo,  Copiap6,  and  other  places  in  Chile,  and  in  a  few  mines  m 
California,  Arizona,  and  Colorado, 



The  blende  group  of  minerals  comprises  a  series  of  compounds  whose 
general  formula  like  that  of  the  galena  group  is  RQ  In  the  blendes  R 
stands  for  Zn,  Cd,  Mn,  Ni  and  Fe  and  Q  for  S,  Se  and  Te 

The  blendes  are  ail  transparent  or  translucent  minerals  of  a  lighter 
color  than  galena  They  constitute  an  isodimorphous  group  of  a  dozen 
or  more  members  crystallizing  in  the  tetrahedral  division  of  the  regular 
system  (hextetrahedral  class),  and  in  hemimorphic  holohedral  forms  of 
the  hexagonal  system  (dmexagonal-pyramidal  class)  The  group  may 
be  divided  into  two  subgroups  known  respectively  as  the  sphalerite 
and  the  wurtzite  groups 


The  most  important  member  of  this  division  of  the  blende  group  is 
the  mineral  sphalerite.  This,  like  the  other  less  well  known  members, 
crystallizes  in  the  hemihedral  division  of  the  regular  system  with  various 
tetrahedrons  as  prominent  forms  The  other  members  of  the  group 
are  alabandite  (MnS),  and  an  isomorphous  mixture  of  FeS  and  NiS, 

Sphalerite  (ZnS) 

Sphalerite,  one  of  the  very  important  zinc  ores  and  one  of  the  most 
interesting  minerals  from  a  crystallographic  standpoint,  occurs  in  amor- 
phous and  crystalline  masses  and  in  handsome  crystals  and  crystal  groups 
Botryoidal  and  other  imitative  masses  are  common 

Pure  white  sphalerite  consists  of  67  per  cent  of  Zn  and  23  per  cent  of 
sulphur  The  colored  varieties  usually  contain  traces  of  silver,  iron, 
cadmium,  manganese  and  other  metals  Sometimes  the  proportion  of 
the  impurities  is  so  large  that  the  mineral  containing  them  is  regarded  as 
a  distinct  variety  Two  analyses  of  American  sphalerites  are  as  follows 

S  Zn      Cd      Fe  Total 

Franklin  Furnace,  N  J  32  22        67  46     tr  99  68 

Jophn,  Mo  32  93        66  69  42  100  04 

The  hemihedral  condition  of  sphalerite  is  shown  in  the  predominance 
of  tetrahedrons  among  its  crystal  forms  and  by  the  symmetry  of  its 

-Q3.      _ 

etched  figures  (Fig.  33).    Its  most  common  forms  are  — ~(321)  and 
other  hextetrahedrons,  ±—(221),  ^-(331)  and  other  deltoid-dodeca- 



hedrons  and  ±303(311)  and  other  tristetrahedrons  In  addition, 
ooO<»(ioo)  and  ooO(no)  are  quite  common  (Fig  34)  Twins  are 
abundant  Their  twinning  plane  is  0  and  their  composition  face  either 
0  (Fig  35),  or  a  plane  perpendicular  to  this  Through  twinning,  the 
crystals  often  assume  a  rhombohedral  habit 

The  cleavage  of  sphalerite  is  perfect  pardlel  to  ooO(no)  From  a 
compact  mass  of  the  mineral  a  fairly  good  dodecahedron  may  some- 
times be  split  Its  fracture  is  conchoidal  When  pure  the  mineral  is 
transparent  and  colorless  As  usually  found,  however,  it  is  yellow, 
translucent  and  black,  brown,  or  some  shade  of  red  Its  streak  is 
brownish,  yellow  or  white.  The  yellow  masses  look  very  much  like 

FIG  33 

FIG  34 

FIG  35 

FIG   33  — Tetrahedral  Crystal  of  Sphalerite  Bounded  by  oo  0  °o  (101)  and  ±O  (in 
and  ill),  Illustrating  the  Fact  that  Its  Octahedral  Faces  Fall  into  Two  Groups 

FIG  34  —Sphalerite  Crystal     oo  0,  no  (<*),  and-f —-,  311  (m) 
FIG  35  — Sphalente  Octahedron  Twinned  about  0(ni) 

lumps  of  rosin.  The  hardness  of  sphalerite  is  between  3  5  and  4,  and  its 
density  about  4  Its  luster  is  resinous  The  minei  al  is  difficultly  fusible, 
and  is  a  nonconductor  of  electricity  Its  index  of  refraction  (ri)  for 
yellow  light  is  2  369. 

Sphalerite  when  powdered  always  yields  tests  for  sulphur  under 
proper  treatment  On  charcoal  it  volatilizes  slowly,  coating  the  coal 
with  a  yellow  sublimate  when  hot,  turning  white  on  cooling  When 
moistened  with  a  dilute  solution  of  cobalt  nitrate  and  heated  m  the 
reducing  flame,  the  white  coating  of  ZnO  turns  green  The  mineral  dis- 
solves in  hydrochloric  acid,  yielding  sulphuretted  hydrogen 

By  oxidation  sphalerite  changes  into  the  sulphate  of  zinc,  and  by 
other  processes  into  the  silicate  of  zinc,  calamine,  or  the  carbonates, 
smithsonite  and  hydrozincite. 


Syntheses  —Sphalerite  crystals  have  been  made  by  the  action  of 
upon  zinc  chloride  \  apor  at  a  high  temperature  They  are  also  often 
produced  in  the  flues  of  furnaces  in  which  ores  containing  zinc  and  sul- 
phur are  roasted 

Occurrence  and  Origin  —  Sphalerite  occurs  disseminated  through  lime- 
stone, in  streaks  and  irregular  masses  in  the  same  rock,  and  in  veins  cut- 
ting crystalline  and  sedimentary  rocks  It  is  often  associated  with 
galena  The  material  in  the  veins  is  often  crystallized  Here  it  is  asso- 
ciated with  chalcopynte  (CuFeS2),  fluonte  (CaF2),  bante  (BaSCX), 
sidente  (FeCOs),  and  silver  ores  When  in  veins  it  is  in  some  cases  the 
result  of  ascending  hot  waters  and  in  other  cases  the  product  of  down- 
ward percolating  meteoric  water.  Much  of  the  disseminated  ore  is  a 
metamorphic  contact  deposit. 

Localities  —  Crystallized  sphalerite  is  found  abundantly  at  Alston 
Moor,  Cumberland,  England,  at  vanous  places  in  Saxony,  in  the  Bin- 
nenthal,  Switzerland;  at  Broken  Hill,  N  S  Wales,  and  in  nearly  all 
localities  for  galena.  Handsome,  transparent,  deavable  masses  are 
brought  from  Pilos  de  Europa,  Santander,  Spain.  Stalactites  are 
abundant  near  Galena,  111 

The  principal  deposits  of  economic  importance  in  America  are  those 
in  Iowa,  Wisconsin,  Missouri  and  Kansas,  where  the  sphalerite  is  asso- 
ciated with  other  zinc  compounds  and  with  galena  forming  lodes  in 
limestone,  and  at  the  silver  and  gold  mines  of  Colorado,  Idaho  and  Mon- 

Extraction  of  the  Metal  —  In  order  to  obtain  the  metal  from  sphalerite, 
the  ore  is  usually  first  concentrated  by  flotation  or  other  mechanical 
processes.  The  concentrates  are  then  converted  into  the  oxide  by  roast- 
ing and  the  impure  oxide  is  mixed  with  fine  coal  and  placed  in  clay  retorts 
openmg  into  a  condenser.  These  are  gradually  heated  The  oxide  is 
reduced  to  the  metal,  which  being  volatile  distils  over  into  the  con- 
denser, where  it  is  safely  caught.  Other  processes  are  based  on  wet 
chemical  methods 

Uses  of  Zinc  —  Zinc  is  used  extensively  in  galvanizing  iron  wire  and 
sheets  It  is  also  employed  in  the  manufacture  of  important  alloys 
such  as  brass,  and  in  the  manufacture  of  zmc  white,  which  is  the  oxide 
(ZnO),  and  other  pigments  A  solution  of  the  chloride  is  used  for  pre- 
serving timber.  Argentiferous  zinc  is  the  source  of  a  considerable  quan- 
tity of  silver. 

Production  —  The  figures  showing  the  quantity  of  sphalerite  pro- 
duced in  the  zinc-producing  countries  are  not  available  The  total 
amount  of  metallic  zmc  produced  in  the  year  1912  was  1,070,045  tons, 


valued  at  $44,699,166,  of  which  the  United  States  produced  from  domestic 
ores  323,907  tons,  and  in  addition  used,  in  the  making  of  zinc  compounds, 
about  55,000  tons  Of  this  aggregate,  Missouri  produced  about  149,560 
tons  Most  of  the  metal  was  obtained  from  sphalerite,  but  a  large 
part  came  from  other  ores  The  quantity  of  silver  produced  in  refining 
zinc  ores  was  664,421  oz  ,  valued  at  $408,619 

Alabandite  (MnS)  is  isomorphous  with  sphalerite  It  usually 
occurs,  however,  in  dense  granular  aggregates  of  an  iron-gray  color 
Its  streak  is  dark  green  It  is  opaque  and  brittle  Its  hardness  is  3-4 
and  density  39  It  is  not  an  electrical  conductor  When  heated  on 
charcoal  in  the  reducing  flame  it  changes  to  the  brown  oude  of  man- 
ganese and  finally  melts  to  a  brown  slag  It  is  soluble  ui  dilute  HC1 
with  the  evolution  of  EkS  Alabandite  occurs  with  other  sulphides  at 
Kapnik,  Hungary,  at  Tarma,  Peru,  at  Puebla,  Mexico,  and  m  the 
United  States  at  Tombstone,  Arizona,  and  on  Snake  River,  Summit  Co  , 

Pentlandite  ((Fe  Ni)S)  may  belong  to  this  group  Iron  is  frequently 
found  in  crystallized  sphalerite  Its  sulphide,  therefore,  may  be  isomor- 
phous with  sphalerite,  in  \\hich  case  pentlandite,  which  is  probably  an 
isomorphous  mixture  of  NiS  and  FeS,  would  also  belong  m  the  sphal- 
erite group  The  mineral  occurs  in  light  bronzy  yellow,  granular  masses 
with  a  distinct  octahedral  cleavage,  a  hardness  of  3  5-5  and  a  density  of 
46  It  is  a  nonconductor  of  electricity  Pentlandite  occurs  with 
chalcopynte  (CuFeS2)  and  pyrrhotite  (FerSg),  at  Sudbury,  Ontario, 
where  it  is  probably  the  constituent  that  furnishes  most  of  the  nickel 
(seep  92) 

It  is  distinguished  from  pyrrhotite,  which  it  resembles  in  appearance, 
by  its  cleavage  and  the  fact  that  it  is  not  magnetic  Moreover,  it 
weathers  to  a  brassy  yellow  color,  while  pyrrhotite  weathers  bronze 


The  wurtzite  group  comprises  only  two  or  three  members,  wurt.iie 
(ZnS),  greenoMe  (CdS),  and  possibly  pyrrhottte  (FenSH+1)     All  crys- 
tallize m  the  holohedral  division  of  the  hexagonal  system  and  the  first 
two  are  unquestionably  heimmorphic  (dihexagonal  pyramidal  class) 
Pyrrhotite  is  the  most  common. 

Wurtzite  (ZnS)  is  one  of  the  dimorphs  of  ZnS,  sphalerite  being  the 
other.  It  occurs  in  brownish  black  crystals,  m  masses  and  m  fibers 


Its  crystals  are  combinations  of  ooP(ioib)  with  2^(2021)  and 
oP(oooi)  at  one  end,  and  a  series  of  steeper  pyramids  at  the 
other  Their  axial  ratio  is  i :  8175  The  a&gk  ion  Aoili=4o°  9', 

2P(022l)  A2P(022I)  =  52°  2Jf 

The  mineral  is  brownish  black  to  brownish  yellow  and  its  streak 
is  brown  Its  hardness  is  between  3  and  4  and  its  sp  gr  is  about  4 
It  conducts  electricity  very  poorly  In  chemical  and  physical  prop- 
erties it  resembles  sphalerite  Its  crystals  ha\e  been  produced  by 
fusing  a  mixture  of  ZnSO.4,  fluonte  and  barium  sulphide  They  are 
frequently  observed  as  furnace  products 

Wurtzite  occurs  as  crystals  at  the  original  Butte  Mine,  Butte, 
Montana,  and  in  a  mine  near  Benzberg,  Rhenish  Prussia,  at  both 
places  associated  \\ith  sphalerite  They  also  occur  \uth  silver  ores  near 
Oruro  and  Chocaya,  Bolivia,  and  near  Quispisiza,  Peru 

Greenockite. — Greenockite  (CdS)  is  completely  isomorphous  with 
wurtzite     Its  crystals  have   an  axial  ratio 
i  '  8109      In   general   habit  they  are  like 
those  of  wurtzite  but  they  contain  many  more 
planes  (Fig    36)      The  angle  ioTiAoiTi  = 
39°  58      Crystals  are  rare  and  small     The 
mineral  usually  occurs  as  a  coating  on  other 
minerals,  especially  sphalerite     Its  color  is 
honey  to  orange-yellow,  its   streak  orange-   FIG  36  —Greenockite  Crys- 
yellow,  and  its  luster  glassy  or  resinous     It      tal    OOP,  ioT<^(w),  aP, 

is  transparent  or  translucent  and  is  brittle  2°?x  ^>  ^IOIJL^and 
TII  j  j  A  i_  ±  °F»  o001  (c)  (The  form 

Its  hardness  is  3-3  5  and  density  about  4  9       ip>  Iol2  (l)  ls  often  pres- 

Its   index    of    refraction    w=2  688      When      ent  at  the  upper  end  of 

heated  in  the  closed  tube  it  becomes  carmine,      the  crystals ) 

but  it  changes  to  its  original  color  on  cooling. 

It  yields  the  usual  reactions  for  sulphur  and  cadmium,  and  dissolves 

in  HC1,  yielding  H2S 

Crystals  have  been  obtained  by  melting  a  mixture  of  CdO,  BaS, 
and  CaF2,  and  by  heating  cadmium  in  an  atmosphere  of  EfeS  to  near 
fusing  point  The  mineral  is  a  common  furnace  product  Greenockite 
crystals  occur  with  prenmte  at  Bishoptown,  Scotland,  and  as  coatings 
on  sphalerite  in  the  zinc  regions  of  Missouri  and  Arkansas,  and  at 
Fnedensville,  Pennsylvania, 


Pyrrhotite  (FenSn+i) 

Pyrrhotite,  or  magnetic  pyrite,  occupies  the  anomalous  position 
of  being  one  of  the  most  important  ores  of  nickel,  whereas  it  is  essen- 
tially a  sulphide  of  iron     The  name  is  really  applied  to  a  series  of 
compounds  whose  composition  ranges  between   FesSo  and  Feu>Si7 
The  crystallized  material  is  in  some  cases  FerSs,  and  in  others,  FenSi2 
It  is  probably  a  solid  solution  of  FeS2  or  S  in  the  sulphide  of  iron  (FeS) 
As  usually  found,  pyrrhotite  is  in  bronze-gray  granular  masses,  that 
tarnish  rapidly  to  bronze  on  exposure  to  the  air     Good  crystals  of 
the  mineral  are  rare. 

Analyses  of  pyrrhotite  vary  widely  The  percentages  of  Fe  and  S 
corresponding  to  FeySs  are  Fe,  60  4,  S,  39  6,  and  those  corresponding 
to  FenSi2  are  Fe,  61  6,  S,  38  4  Much  of  the  mineral  contains  in  addi- 
tion to  the  iron  and  sulphur  sufficient  nickel  to  render  it  an  ore  of  this 
metal,  but  it  is  probable  that  the  nickel  is  present  in  pentlandite  (see 
p  90)  or  some  other  nickel  compound  embedded  in  the  pyrrhotite 

Analyses  of  pyrrhotite  from  various  localities  are 

S  Fe  Co            Ni  Total 

Schneeberg,  Saxony           39  10  6r  77  tr  100  87 

Brewster,  NY                  37  98  61  84                            25  100  07 

Sudbury,  Ontario              38  91  56  39                        4  66       99  96 

Gap  Mine,  Penn.               38  59  55  82                        5  59  100  oo 

The  few  crystals  of  pyrrhotite  known  are  distinctly  hexagonal  in 
habit  with  a    c=i    i  7402     They  are  com- 
monly tabular  or  acutely  pyramidal,  but  it 
has  not  been  established  that  they  are  hemi- 
morphic,  although  the  almost  universal  pres- 
ence of  FeS  in   crystals  of  wurtzite  would 
FIG  37 -Pyrrhotite  Crystal    mdlcate  that  the  two  substances  are  isomor- 
oP,  oooi  (c),  P,  ion  (s);      ,  _,     ^  ,    ,  .  f 

4P,  4041  («),  and  COP,  Phous     The  tabular  crystals  possess  a  broad 
I0lo  (m)  basal  plane,  which  surmounts  hexagonal  prisms 

ooP(ioTo)  and  oop2(ii2o);  and  a  series  of 

pyramids,  of  which  2P(2O2i),  JP(ioT2),  P(ioli)  and  P2(ri22)  are  the 
most  frequent     (Fig  37  )     The  angle  loli  AoiTi  =  S3°  «; 

The  cleavage  of  pyrrhotite  is  not  always  equally  distinct  When 
marked  it  is  parallel  to  ooP2(ii2o)  There  is  also  often  a  parting 
parallel  to  the  base  Its  fracture  is  uneven  The  mineral  is  brittle. 
It  is  opaque,  and  has  a  metallic  luster  Its  color  varies  between  bronze- 


yellow  and  copper-red,  and  its  streak  is  grayish  black  Its  hardness  is 
a  little  less  than  4  and  its  density  about  4  5  All  specimens  are  magnetic 
but  the  magnetism  varies  greatly  in  intensity,  being  at  a  maximum  in 
the  direction  of  the  vertical  axis  The  mineral  is  a  good  conductor  of 

Pyrrhotite  gives  the  usual  reactions  for  iron  and  sulphur,  and  some- 
times, in  addition,  the  reactions  for  cobalt  and  nickel  It  is  decom- 
posed by  hydrochloric  acid  with  the  evolution  of  EbS,  which  may 
easily  be  detected  by  its  odor. 

From  the  many  sulphides  more  or  less  closely  resembling  pyrrhotite 
in  appearance,  this  mineral  may  easily  be  distinguished  by  its  color 
and  density  and  by  its  magnetism 

Syntheses — Crystals  may  be  obtained  by  heating  iron  wire  or 
Fes04,  or  dry  FeCk  to  redness  in  an  atmosphere  of  dry  HoS  and  by 
heating  Fe  in  a  closed  tube  with  a  solution  cf  FcCls  saturated  with 

Occurrence,  Locd^t^es  and  Origin — Pyrrhotite  occurs  completely 
filling  vein  fissures,  and  also  as  crystals  embedded  in  other  minerals 
constituting  veins  It  occurs  also  as  impregnations  in  various  rocks 
and  as  a  segregation  in  the  coarse-grained  basic  rock  known  as  nonte, 
where  it  is  believed  to  have  separated  from  the  magma  producing  the 
rock  It  may  also  in  some  cases  be  a  product  of  metamorphism  on  the 
borders  of  igneous  intrusions 

It  is  found  at  Andreasberg,  Harz,  Bodenmais,  Bavaria,  Minas 
Geraes,  Brazil,  various  points  in  Norway  and  Sweden,  and  on  the 
lavas  of  Vesuvius  In  North  America  crystals  occur  at  Standish,  Maine, 
at  Trumbull,  Monroe  Co ,  N  Y  ,  and  at  Elizabethtown,  Ontario 
The  mineral  has  been  mined  at  Ducktown,  Tenn  ,  at  Ely,  Vermont, 
and  at  Gap  Mine,  Lancaster  Co  ,  Penn 

Its  mines  at  present,  however,  are  at  Sudbury,  in  Ontario,  where  the 
mineral  is  associated  with  magnetite,  chalcopynte  and  pentlandite 
((Fe  Ni)S)  on  the  lower  border  of  a  great  mass  of  igneous  rock  (norite). 
Besides  these  there  are  present  also  embedded  in  the  pyrrhotite 
small  quantities  of  other  minerals,  so  that  the  ore  as  mined  is  very 

Pyrrhotite  is  sometimes  found  altered  to  pyrite,  to  limomte  and  to 
siderite  (FeC03) 

Extraction — Pyrrhotite  is  crushed  and  roasted  to  drive  off  the 
greater  portion  of  the  sulphur  It  is  then  placed  in  a  furnace  and 
smelted  with  coke  and  quartz  The  nickel,  copper  and  some  of  the 
iron,  together  with  some  of  the  fused  sulphides,  collect  as  a  matte  in  the 


bottom  of  the  furnace  from  which  it  is  withdrawn  from  time  to  time 
The  matte  is  next  roasted  to  transform  the  iron  it  contains  into  oxides 
and  the  remaining  nickel  and  copper  are  separated  by  patented  or  secret 

Uses  —The  mineral  is  sometimes  worked  for  the  sulphur  it  con- 
tains Its  principal  use,  however,  is  as  a  source  for  nickel,  nearly  all  of 
this  metal  used  in  America  coming  from  the  nickehferous  variety  found 
at  Sudbury,  Ontario 

The  metal  nickel  has  come  into  extensive  use  in  the  past  few  years 
in  connection  with  the  manufacture  of  armor  plate  for  warships  The 
addition  of  a  few  per  cent  of  nickel  to  steel  hardens  it  and  increases 
its  strength  and  elasticity 

Nickel  is  also  extensively  used  in  mckel-platmg  and  in  the  manufac- 
ture of  alloys  German  silver  is  an  alloy  of  nickel,  copper  and  zinc  The 
nickel  currency  of  the  United  States  contains  about  25  per  cent  Ni  and 
75  per  cent  Cu  Monel  metal  is  a  silver-white  alloy  containing  about 
75  per  cent  Ni,  i  per  cent  Fe  and  29  per  cent  Cu  It  is  stronger  than 
ordinary  steel,  takes  a  brilliant  finish  and  is  impervious  to  acids  It  is 
made  directly  at  Sudbury,  Ont ,  by  smelting 

Production  —The  production  of  pyrrhotite  and  chalcopyrite  (CuFeS) 
at  the  Sudbury  mines  in  1912  amounted  to  737,584  short  tons  The 
value  of  the  matte  produced  was  $6,303,102,  and  the  value  of  nickel  con- 
tained in  it  was  about  $16,000,000  About  half  of  the  nickel  was  used 
in  America,  the  remainder,  amounting  to  $8,515,000,  was  exported,  after 
being  refined  in  the  United  States  Formerly  the  United  States  pro- 
duced a  considerable  quantity  of  nickel  from  domestic  ores,  most  of 
it  from  pyrrhotite,  but  the  mines  have  been  closed  down  within  the  past 
few  years.  It  is,  however,  produced  as  a  by-product  in  the  refining 
of  copper  ores  to  the  amount  of  about  325  tons  annually,  This  is  worth 
about  $260,000  (see  also  p,  400). 


This  group  comprises  sulphides,  arsenides  and  antimonides  of  nickel. 
It  includes  the  minerals  millmte  (NiS),mccohte  (NiAs),  ante  (Ni(Sb  •  As)) 
bwthauptite  (NiSb)  and  a  few  others  Of  these  only  millente  and  nic- 
colite  are  at  all  common  The  minerals  all  crystallize  m  the  hexagonal 
system,  possibly  in  the  rhombohedral  division  (ditrigonal  scalenohedral 
class).  Well  defined  crystals  are,  however,  rare  and  often  capillary  so 
that  their  symmetry  has  not  been  determined  with  certainty. 


Mfflerite  (NiS) 

Millerite  is  easily  recognized  by  its  brass-yellow  color  It  occurs 
most  frequently  in  slender  hair-like  needles,  often  aggregated  into  tufts 
or  radial  groups,  or,  woven  together  like  wads  of  hair,  forming  coatings 
on  other  minerals 

Pure  millente  contains  35  3  per  cent  sulphur  and  64.6  per  cent  nickel 
It  frequently  contains  also  a  little  Co  and  Fe. 

Crystals  are  thin,  acicular  or  columnar  with  prismatic  and  rhom- 
bohedral  faces  predominating,  and  an  axial  ratio  of  i  330,  or  of  i  :  9886 
if  the  rhombohedron  311(0331)  is  taken  as  the  ground  form 

The  mineral  is  elastic  Its  hardness  is  3-3  5  and  density  about  5  5. 
It  is  opaque  and  brassy  yellow  Its  streak  is  greenish  black.  It  is  an 
excellent  conductor  of  electricity 

The  mineral  yields  sulphurous  fumes  in  the  open  tube.  After  roast- 
ing it  gives,  with  borax  and  microcosmic  salt,  a  violet  bead  when  heated 
in  the  oxidizing  flame  of  the  blowpipe  On  charcoal  with  NaaCOs  it 
yields  a  magnetic  globule 

Synthesis  —  Bunches  of  yellow  acicular  crystals  of  N1S  have  been 
formed  by  treatment  of  a  solution  of  NiSO^  with  H^S,  under  pressure. 

Localities  —  Millerite  occurs  as  long  acicular  crystals  in  cavities  in 
other  minerals  at  Joachimthal,  in  Bohemia,  and  at  many  places  in 
Saxony  In  the  United  States  it  forms  radiating  groups  in  cavities  in 
hematite  (F&Os)  at  Antwerp,  NY  At  the  Gap  Mine,  Lancaster  Co  , 
Penn  ,  it  forms  coatings  on  other  minerals  and  at  St  Louis,  Mo  and 
at  Milwaukee,  Wis  ,  it  occurs  in  delicate  tangled  tufts  in  geodes  in  lime- 
stone, Nowhere  does  it  occur  in  sufficient  quantity  to  constitute  an  ore. 

Niccolite  (NiAs) 

Niccolite  usually  occurs  massive,  though  crystals  are  known  It  is 
of  economic  importance  only  in  a  few  localities 

Theoretically,  the  mineral  contains  56  10  per  cent  As  and  43  90  per 
cent  Ni,  but  as  usually  found  it  contains  also  Sb,  S,  Fe  and  often  small 
quantities  of  Co,  Cu,  Pb  and  Bi 

Its  crystals,  which  are  rare,  are  hexagonal  and  hemimorphic  (prob- 
ably dihexagonal  pyramidal  class),  with  a  :  c=i  :  8194  The  prism 
ooP(ioTo),  and  oP(oooi)  are  the  predominant  forms,  with  the 
pyramids  P(ioTi)  and  ^(5057)  less  well  developed  The  angle 

The  mineral  is  pale  copper-red  and   opaque      It  has  a  brownish 


black  streak.  Its  hardness  is  about  5  and  its  density  7  6  The  surfaces 
of  nearly  all  specimens  are  tarnished  with  a  grayish  coating  The  min- 
eral is  a  good  conductor  of  electricity 

In  the  open  tube  mccohte  yields  arsenic  fumes  and  often  traces  of 
862  On  charcoal  with  Na2COs  it  yields  a  metallic  globule  of  nickel 
It  dissolves  in  HNOs  with  the  precipitation  of  AsgOa  The  apple-green 
solution,  thus  produced,  becomes  sapphire-blue  on  addition  of  ammonia 

Its  peculiar  light  pink  color  and  its  reactions  for  arsenic  and  nickel 
distinguish  mccohte  from  all  other  minerals,  except,  perhaps,  breit- 
kaupttte,  which,  however,  contains  antimony 

Occurrence  — Niccohte  occurs  principally  in  veins  in  crystalline 
schists  and  in  metamorphosed  sedimentary  rocks,  associated  with  silver 
and  cobalt  sulphides  and  arsenides 

Local^foes  — The  principal  locality  for  mccohte  in  North  America  is 
Cobalt,  Ontario,  where  it  is  found  with  native  silver  and  silver,  cobalt, 
and  other  nickel  compounds,  all  of  which  are  thought  to  have  been  de- 
posited by  hot  waters  emanating  from  a  mass  of  diabase  In  Europe  it 
is  abundant  at  Joachimsthal  in  Bohemia,  and  at  a  number  of  other 
places  in  small  quantity 

Although  rich  in  nickel,  the  mineral  is  not  used  as  an  ore  at  present, 
except  to  a  very  minor  extent,  most  of  the  nickel  of  commerce  being 
obtained  from  other  compounds  (see  p  94) 

Breithauptite  (NiSb)  is  rare  It  is  of  a  light  copper-red  color,  much 
brighter  than  that  of  mccohte,  and  its  streak  is  reddish  brown  Its  hard- 
ness is  5  5  and  density  about  7  9  Its  crystals  are  hexagonal  tables 
with  an  axial  ratio  i  i  294,  and  a  distinct  cleavage  parallel  to  oP(ooi) 
It  usually  occurs  m  dendritic  groups,  m  foliated  and  finely  granular 
aggregates  and  in  dense  masses  It  is  a  frequent  furnace  product,  when 
ores  containing  Ni  and  Sb  are  smelted  It  is  found  at  Andreasberg,  Harz , 
at  Sarrabus,  m  Sardinia,  at  Cobalt,  Ont ,  and  at  a  few  other  places  It 
is  distinguished  from  mccohte  by  its  deeper  color  and  its  content  of  Sb. 

Covelhte  (CuS) 

Covellite,  or  indigo  copper,  is  the  cupric  sulphide,  chalcocite  being 
the  corresponding  cuprous  salt  It  is  called  indigo  copper  because  of 
the  deep  blue  color  of  its  fresh  fracture.  It  is  often  mixed  with  other 
copper  compounds  from  which  it  has  been  derived  by  alteration  It 
usually  occurs  massive,  but  crystals  are  known  It  is  an  unimportant 
ore  of  copper. 


The  theoretical  composition  of  the  mineral  is  33  56  per  cent  S, 
66  44  per  cent  Cu  It  usually,  however,  contains  also  a  little  iron  and 
often  traces  of  lead  and  silver 

Crystals  of  covellite  are  not  common.  They  are  hexagonal  \\ith 
a  c-i  3  972  and  their  habit  is  usually  tabular  The  forms  observed 
are  oP(oooi),  oo  P(iolo),  P(ioTi)  and  JP(ioT4)  icTi  /\oi Ti  =  77°  42'. 

The  mineral  has  one  perfect  cleavage  parallel  to  oP(oooi)  In 
thin  splinters  it  is  flexible  Its  hardness  is  i  5-2  and  density  about 
4  6  Its  color  is  dark  blue  and  its  streak  lead-gray  to  black  It  is 
opaque,  with  a  luster  that  is  sometimes  nearly  metallic,  but  more 
frequently  dull  It  is  a  good  electrical  conductor 

The  blowpipe  reactions  of  covellite  are  like  those  of  chalcocite,  with 
these  exceptions  Covellite  burns  ^ith  a  blue  flame  when  heated  on 
charcoal,  and  yields  a  sublimate  of  sulphur  in  the  closed  tube 

Covellite  is  distinguished  from  other  minerals  than  chalcocite  by 
its  reactions  for  Cu  and  S  and  the  absence  of  reactions  for  Fe.  It  is 
distinguished  from  chalcocite  by  its  color  and  density  and  by  the  fact 
that  it  ignites  on  charcoal 

Syntheses  — The  treatment  of  green  copper  carbonate  with  water 
and  EkS  in  a  closed  tube  at  8o°-9o°  yields  small  grains  of  covellite 
The  mineral  has  also  been  produced  by  the  action  of  HsS  upon  vapor 
of  CuCl2,  and  by  treating  sphalerite  with  a  solution  of  copper  sulphate 
in  a  sealed  glass  tube  containing  C02  at  a  temperature  of  iso°-i6o° 
for  two  days 

Localities  and  Origin— The  mineral  is  comparatively  rare  It  is 
abundant  in  Chile  and  Bolivia  and  at  Butte,  Mont ,  and  is  found  in 
crystals  on  the  lava  of  Vesuvius  and  elsewhere  It  usually  occurs  as 
an  alteration  product  of  other  copper-sulphur  compounds,  especially  in 
the  zone  of  secondary  enrichment  of  copper  veins 

Uses — It  is  mined  with  other  compounds  and  used  as  a  source 
of  copper, 


This  group  comprises  sulphides,  selenides  and  tellundes  of  mercury 
The  group  is  dimorphous,  with  its  members  crystallizing  in  henuhedrons 
of  the  isometric  system  (hextetrahedral  class)  and  in  tetartohedrons 
of  the  hexagonal  system  (trigonal  trapezohedral  class)  The  isometric 
HgS  is  known  as  metacmnabante  and  the  hexagonal  form  as  cinnabar 
Only  the  latter  is  important  In  addition  to  these  are  known  the  rare 
compounds  onofnte  (Hg(S  Se)),  tiemanmte  (HgSe)  and  coloradcnte 
(HgTe),  all  of  which  are  isometric 



Cinnabar  (HgS) 

Cinnabar  is  the  only  compound  of  mercury  that  occurs  in  sufficient 
quantity  to  constitute  an  important  ore  Nearly  all  of  the  mercury, 
or  quicksilver,  in  the  world  is  obtained  from  it  The  mineral  occurs 
both  crystallized  and  massive  The  ore  is  a  red  crystalline  mass  that 
is  easily  distinguished  from  all  other  red  minerals  by  its  peculiar  shade  of 
color  and  its  great  weight. 

Theoretically,  it  contains  13  8  per  cent  S  and  86  2  per  cent  Hg 
Massive  cinnabar  is,  however,  usually  impure  through  the  admixture 
of  clay,  iron  oxides  or  bituminous  substances  Occasionally  the  quan- 
tity of  organic  material  present  is  so  large  that  the  mixture  is  inflam- 

Though  cinnabar  is  usually  granular,  massive  or  earthy,  it  some- 
times occurs  beautifully  crystallized 
in  small  complex  and  highly  modi- 
fied hexagonal  crystals  that  exhibit 
tetartohedral  forms  (trigonal  trape- 
zohedral  class)     Usually  the  crys- 
tals are  rhombohedral  or  prismatic 
m    habit      Their    axial    ratio    is 
i  .  i  1453       Planes    belonging    to 
more  than  100  distinct  forms  have 
been  observed,  but  the  crystals  on 
which  they   occur   aie   usually  so 
small  that  few  of  them  are  of  im- 
portance as   distinguishing   charac- 
teristics.   The  prismatic   crystals,  which   are   the  most  common  in 
this  country,  are  often  bounded  by   ooR,  (rolo)    and    £R,   (4045) 
(Fig  38)     Others,  however,  are  very  complicated     Their  cleavage  is 
perfect  parallel  to  oo  R(ioTo). 

The  mineral  is  slightly  sectile  It  is  transparent,  translucent  or 
opaque,  is  of  a  cochineal-red  color,  often  inclining  to  brown,  and  its 
streak  is  scarlet  Its  hardness  is  only  2-2  5  and  its  density  about 
8  i  It  is  circularly  polarizing  and  is  a  nonconductor  of  electricity 
Its  dimorph,  metacinnabante,  on  the  other  hand,  is  a  good  conductor 
The  indices  of  refraction  of  cinnabar  are  co=  2  854,  €==3  201 

When  heated  gently  in  the  open  tube  cinnabar  yields  sulphurous 
fumes  and  globules  of  mercury.  On  charcoal  before  the  blowpipe  it 
volatilizes  completely. 

There  are  only  a  few  minerals  with  which  cinnabar  is  likely  to  be 

FIG  38 -Cinnabar  Crystals  with  «  R, 
iolo  (m),  fR,  4045  (0,  £R,  2025 
(/),  R,  loTi  (0  and  o&,  oooi  (c) 


confused,  since  its  color  and  streak  are  so  characteristic  From  all 
red  minerals  but  realgar  it  may  easily  be  distinguished  by  its  sulphur 
reaction  From  realgar  it  is  distinguished  by  its  great  density  and  its 
greater  hardness 

Pseudomorphs  of  cinnabar  after  stibnite,  dolomite  ((Ca  Mg)COsJ, 
pynte  and  tetrahednte  (a  complicated  sulpho-salt)  have  been  described 

Synthesis  —  Crystals  ha\  e  been  made  b>  heating  mercury  in  an  aque- 
ous solution  of  HbS 

Occurrence  Localities  and  On  gin  —  Cinnabar  is  usually  found  in 
veins  cutting  serpentine,  limestones,  slates,  shales  and  \anous  schists 
It  is  associated  \Mth  gold,  various  sulphides,  especially  pynte  and  mar- 
casite  (FeS2)  calcite  (CaCOs),  barite  (BaSO-i),  fluonte  (CaF2)  and 
quartz  It  is  also  found  impregnating  sandstones  and  other  sedimen- 
tary rocks,  and  sometimes  as  a  deposit  from  hot  springs  Its  deposi- 
tion is  thought  to  be  the  result  of  precipitation  from  ascending  hot 

Crystallized  cinnabar  occurs  at  a  number  of  places  in  Bohemia, 
Hungary,  Serbia,  Austria,  Spam,  California,  Texas,  Nevada,  and  at 
ether  localities  m  Europe  Asia  and  South  America 

The  principal  deposits  of  economic  importance  are  at  Almaden 
in  Spain,  at  Idria  in  the  Province  of  Carmola,  Austria,  at  Bakhmut 
in  southern  Russia,  at  various  points  along  the  Coast  Ranges  in  Cal- 
ifornia, in  Esmeralda,  Humboldt,  Nye  and  Washoe  Counties  in  Nevada, 
at  many  points  in  Oregon  and  Utah,  and  at  Terhngua  in  Texas  The 
mineral  is  also  abundant  in  Peru  and  in  China  but  in  these  countries 
it  has  not  yet  been  mined  profitably  The  California  cinnabar  district 
extends  for  many  miles  along  the  Coast  Ranges,  but  at  only  about  a 
dozen  places  is  the  mineral  mined 

The  Spanish  mines,  near  the  city  of  Cordova,  have  been  worked 
for  many  hundreds  of  years  Much  of  the  ore  is  an  impregnation  of 
sandstone  and  quartzite  —  the  mineral  sometimes  comprising  as  much 
as  20  per  cent  of  the  rock  mined 

Extraction  —  The  metallurgy  of  cinnabar  is  exceedingly  simple  It 
consists  simply  in  roasting  the  ore  alone,  or  mixed  with  limestone,  and 
conducting  the  fumes  into  a  condensing  chamber  that  is  kept  cool. 
The  sulphur  gases  are  allowed  to  escape  through  the  chamber  in  which 
the  mercury  is  collected 

Uses  of  Metal  —  Mercury  finds  many  uses  in  the  arts  Its  most  im- 
portant one  is  in  the  extraction  of  gold  and  silver  by  the  amalgamation 
process  It  is  the  essential  constituent  of  the  pigment  vermilion,  which 
is  a  manufactured  HgS.  In  its  metallic  state  it  is  largely  employed  in 


the  making  of  mirrors,  of  barometers,  thermometers  and  other  physical 
instruments  Some  of  the  salts  are  important  medicinal  preparations 
while  others  are  used  in  the  manufacture  of  percussion  caps 

Production —The  world's  annual  production  of  quicksilver,  all  of 
which  is  obtained  from  cinnabar,  is  not  far  from  4,000  metric  tons  The 
United  States  produced  940  tons  in  1912,  valued  at  $1,053,941  Of  this 
total  California  yielded  20,524  flasks  of  75  Ibs  each,  valued  at  about 
$863,034,  and  Texas  and  Nevada  4,540  flasks  valued  at  $190,907  To 
produce  these  quantities  of  metal  California  mined  I39>347  tons  of  ore 
and  Texas  and  Nevada  16,346  tons  The  California  ore  yielded  n  Ibs 
of  metal  per  ton  and  the  Nevada  and  Texas  ore  20,8  Ibs, 

Metacmnabarite  (HgS)  is  generally  found  as  a  gray-black  massive 
mineral  with  a  black  streak  It  is  brittle,  has  a  hardness  of  3  and  a 
density  of  7  8  It  is  associated  with  cinnabar  at  some  of  the  mines  in 
California  and  Mexico,  and  at  a  few  places  in  other  countries  It  is 
exceedingly  rare. 


The  disulphides,  diselemdes,  ditellundes,  diarsemdes  and  dianti- 
monides  differ  from  the  corresponding  monocompounds  m  that  they 
contain  double  the  quantity  of  S,  Se,  Te  and  Sb  They  are  divisible 
into  two  groups,  one  of  which  comprises  sulphides,  arsenides  and  anti- 
monides  of  iron,  manganese,  cobalt,  nickel  and  platinum,  and  the  other 
the  tellundes  and  selemdes  of  gold  and  silver, 


The  glanz  group  is  an  excellent  illustration  of  an  isodimorphous  group. 
Its  members  are  characterized  by  their  hardness,  opaqueness,  light  color 
and  brilliant  luster.  Hence  the  name  of  the  group  In  composition 
the  minerals  belonging  to  the  group  are  sulphides,  arsenides  or  anti- 
momdes  of  the  iron-platinum  group  of  metals,  with  the  general  formula 
RQ2  in  which  R  is  Mn,  Fe,  Ni,  Co,  Pt,  and  Q=S,  As  and  Sb  The  com- 
position of  the  more  simple  members  may  be  represented  by  the  formula 

Fe/  | ,  and  of  those  in  which  arsenic  or  antimony  replaces  a  part  of  the 

S y 

It  is  probable,  however,  that  some  of  the  cobalt  and  nickel  arsenides 


are  mixtures  and  that  their  indicated  compositions  are  only  approximate 
All  members  of  the  group  are  believed  to  be  dimorphous,  crystallizing 
in  the  isometric  (dyakisdodecahedral  class),  and  in  the  orthorhombic 
systems  (orthorhombic  bipyramidal  class),  though  not  all  have  as  yet 
been  found  in  both  forms  The  most  important  members  of  the  group,  as 
at  present  constituted,  are  as  follows 

Isometric  Orthorhombic 

Pynte  FeSg  Marcasite 

Hauente  MnS2 

FeAsS  Arsenopyrite 

FeAs2  Lolhngite 

CobalMe  CoAsS  Glaucodot 

Gersdor/tte  (Ni  Fe)AsS 

Korymte  (Ni  Fe)(As  Sb  S)2        Wolfachite 

Ullmamte  NiSbS 

Smdtite  CoAs2  Safflonte 

Ckloanthite  NiAs2  Rammdsbergite 

Sperryhte  PtAs2 

The  group  is  divided  into  two  subgroups,  the  regularly  crystallizing 
minerals  forming  the  pynte  group  and  the  orthorhombic  ones  the  mar- 
casite  group  The  most  important  members  of  the  former  group  are 
pynte,  cobaltite,  smaltite  and  chloanthite  The  most  important  members 
of  the  marcasite  group  are  marcastte,  arsenopynte  and  lolhngite. 


The  crystallization  of  the  pyrite  group  is  in  the  parallel  heimhedral 
division  (dyakisdodecahedral  class)  of  the  isometric  system.  The 

occurrence  of  the  form    -  ,  210,  is  so  frequently  seen  on  the  mineral 

pyrite  that  it  has  received  the  name  pyritoid 

The  group  is  so  perfectly  isomorphous  that  a  description  of  the  forms 
on  one  member  is  practically  a  description  of  the  forms  on  all. 

Pynte  (FcS2) 

Pyrite,  one  of  the  most  common  of  all  minerals,  is  found  under  a 
great  variety  of  conditions  as  crystals,  as  crystalline  aggregates  and 
as  crystalline  masses  It  occurs  under  practically  all  conditions  and  in 
all  situations  It  is  easily  recognized  by  its  bright  yellow  color,  its 
brilliant  luster  and  its  hardness, 



Pyrite  containing,  theoretically,  46  6  per  cent  of  iron  and  53  4  per 
cent  of  sulphur  is  usually  contaminated  with  small  quantities  of  nickel, 

FTC  39  —  Group  of  Pyrite  Crystals  in  which  the  Cube  Predominate     The  c 

are  striated  parallel  to  the  edge  between  oo  0  oo  (100)  and  I  —  —  )  ,  (210) 

cobalt,  thallium  and  other  elements     An  auriferous  variety  is  worked 
for  gold,  yielding  in   the  aggregate  a  large  quantity  of  the  precious 

FIG  40  I«K,  4i 

FIG  40  —  Pynte  Crystals  on  which  0  (in)  Predon  mates     o=0,  n  i  and  c 

FIG  41  —  Pynte  Crystal  with  oo  02,  210  (e)  and  0,  in  (a) 

metal     Sometimes  arsenic  is  present  in  small  quantity     Analysis  of 
the  crystals  from  French  Creek,  Penn  ,  gave 

8=5408,  As=o  20,  Fe=44  24,  Co=i  75,  Ni=o  18,  Cu=oos,  =100  50. 



The  number  of  forms  that  have  been  observed  on  pynte  crystals  is 

very  large     Hintze  records  86      The  cube  and  the  pyntoid     ^-^  I 

L    2    J 

FIG    42 — Group  of  Pynte  Crystals  in  \\hich    ooQ2  (210)  Predominates 
Daly- Judge  Mine,  near  Park  City,  Utah     (After  J  W  Bmtfaett ) 


(210)  are  the  most  common  of  these,  though  the  octahedron  and  the 

dodecahedron  are  not  rare     Four  distinct  types  of  crystals  may  be 

recognized,  viz    those  with  the  cubic  (Fig  39), 

the  octahedral  (Fig.  40),  and  the  pyntoid 

habits  (Figs  41  and  42),  and  those  that  are 

interpenetrating  twins  (Fig  43)     The  cubic 

and  the  pyritoid  planes  are   often  striated 

parallel  to  the  edges  between  these  faces    The 

interpenetrating  twins  are  twinned  about  the 

plane  0(ni) 

The  cleavage  of  pynte  is  imperfect  and 
its  fracture  conchoidal.  The  mineral  is 
brittle  Its  hardness  is  6-6  5  and  density 
about  5.  Its  luster  is  very  brilliant  and 
metallic  Its  color  is  brassy  yellow  and  its 

streak  greenish  or  brownish  black  With  steel  it  strikes  fire,  hence  its 
name  from  the  Greek  word  meaning  fire.  It  is  a  good  conductor  of 
electricity  and  is  strongly  thermo-electric. 

FIG  43  — Pynte  Interpene- 
trationTwin  Two  Pyn- 
toids  ( «s  Os,  210)  Twinned 
about  O  in 

In  the  closed  tube  pynte  yields  a  sublimate  of  sulphur  and  a  residue 
that  is  magnetic  On  charcoal  sulphur  is  freed  This  burns  with  the 
blue  flame  characteristic  of  the  substance  The  globule  remaining  after 
heating  for  some  time  is  magnetic  Treated  with  nitric  acid  the 
mineral  dissolves  leaving  a  flocculent  residue  of  sulphur,  which  when 
dried  and  heated  may  readily  be  ignited 

Pynte  in  some  of  its  forms  so  closely  resembles  gold  that  it  is  often 
known  as  fool's  gold  There  is,  of  course,  no  difficulty  in  distinguishing 
between  the  two  metals,  since  pyrite  contains  sulphur  and  is  soluble  in 
nitric  acid,  while  gold  contains  no  sulphur  and  is  insoluble  in  all  simple 

The  mineral  is  most  easily  confounded  with  chako  pynte  (CuFeS>), 
though  the  difference  in  hardness  of  the  two  easily  serves  to  distinguish 
them  Chalcopynte  may  be  readily  scratched  with  a  knife  blade  or  a 
file,  while  pyrite  resists  both  The  latter  mineral,  moreover,  contains 
no  copper 

Syntheses — Small  crystals  of  pyrite  are  produced  by  the  action 
of  HaS  on  the  oxides  or  the  carbonate  of  iron  enclosed  in  a  sealed  tube 
heated  to  8o°-9o°,  also  by  the  passage  of  EbS  and  FeCla  vapors  through 
a  red-hot  porcelain  tube. 

Occurrence  and  Origin— Pynte  occurs  in  veins  and  as  grains  or 
crystals  embedded  in  all  kinds  of  rocks.  In  rocks  it  usually  appears  as 
crystals,  but  in  vein-masses  it  may  appear  either  as  crystals,  with  other 
minerals,  or  as  radiating  or  structureless  masses  occupying  entirely  the 
vein  fissures  In  slates  it  often  occurs  in  spheroidal  nodules  and 
concretions  of  various  forms,  and  also  as  embedded  crystals.  The 
mineral  is  the  product  of  igneous,  metamorphic  and  aqueous  agencies 

Pyrite  weathers  readily  to  hmonite.  In  ore  bodies  near  the 
surface  it  is  oxidized.  A  portion  of  the  mineral  changes  to  FeSQt 
which  percolates  downward  and  aids  in  the  concentration  of  any 
valuable  metals  that  may  be  present  m  small  quantity  in  the  ore. 
Another  portion  of  the  iron  remains  near  the  surface  in  the  form  of 
lunonite  This  covering  of  oxidized  material  is  known  as  the  "  gossan  " 
and  it  is  characteristic  of  all  pyrite  deposits 

Localities  — Pynte  crystals  are  so  widely  distributed  that  but  very 
few  of  its  most  important  occurrences  may  be  mentioned  here  In  the 
mines  of  Cornwall,  Eng ,  and  in  those  on  the  Island  of  Elba  very  large 
crystals  are  found  Fine  crystals  also  come  from  many  different  places 
in  Bohemia,  Hungary,  Saxony,  Peru,  Norway,  and  Sweden 

In  the  United  States  the  finest  crystals  are  at  Schoharie  and  Rossie, 
N  Y ;  at  the  French  Creek  mines  in  Chester  Co ,  and  at  Cornwall, 


Lebanon  Co  ,  Penn  ,  and  near  Greensboro  and  Guilford  Co  ,  X  Carolina 
Massive  pyrite  occurs  in  great  deposits  at  the  Rio  Tmto  mines  in 
Spain,  at  Rowe,  Mass  ,  in  St  Lawrence  and  Ulster  counties,  X  Y  , 
in  Louise  Co  ,  Va  ,  and  in  Pauldmg  Co  ,  Ga  Much  of  the  massive 
pynte  in  the  veins  of  Colorado,  California  and  of  the  southern  states, 
from  Virginia  to  Alabama,  is  auriferous  and  much  of  it  is  mined  for  the 
gold  it  contains 

Uses — Pynte  is  used  principally  in  the  manufacture  of  sulphuric 
acid  The  mineral  is  burned  in  furnaces  and  the  862  gases  thus  result- 
ing are  carried  to  condensers  \\here  they  are  oxidized  by  fineh  divided 
platinum  or  by  the  oxides  of  nitrogen  The  residue,  which  consists 
largely  of  Fe20s,  is  sometimes  smelted  for  iron  or  made  into  paint 
This  residue  also  contains  the  gold  and  other  \aluable  metals  that  may 
have  been  in  the  original  pyrite. 

The  sulphuric  acid  obtained  from  pyrite  enters  into  many  manu- 
facturing processes  The  greater  portion  of  it  is  consumed  in  the 
artificial  fertilizer  industry 

Production  — Pyrite  is  mined  in  the  United  States  in  Franklin  Co  , 
Mass ,  in  Alameda  and  Shasta  Counties,  California,  in  Louisa,  Pulaski 
and  Prince  William  Counties,  Va ,  in  Carroll  Co  ,  Ga  3  in  St  Lawrence 
Co ,  N  Y  ,  m  Clay  Co ,  Alabama,  and  at  the  coal  mines  in  Ohio. 
Illinois  and  Indiana  where  it  is  a  by-product  The  total  production 
of  the  United  States  in  1912,  amounting  to  330,928  long  tons,  was 
\alued  at  $1,334,259  Virginia  is  by  far  the  largest  producer  In 
addition  to  this  quantity  the  trade  consumed  970,785  tons  of  imported 
ore,  most  of  which  came  from  Spain,  and  utilized  the  equivalent  of 
260,000  tons  of  pynte  m  the  shape  of  low  grade  sulphide  copper  ores 
from  Ducktown,  Tenn ,  and  zinc  sulphide  concentrates  from  the  Mis- 
sissippi Valley  and  elsewhere  for  the  manufacture  of  sulphuric  acid. 
The  total  amount  of  sulphuric  acid  manufactured  in  the  United  States 
during  1912  was  2,340,000  short  tons,  valued  at  $18,338,019  The  total 
world  production  of  pyrite  is  about  2,000,000  tons  annually 

Small  quantities  of  the  mineral  are  also  mined  for  local  consumption 
in  Lumpkin  Co ,  Georgia,  and  near  Hot  Springs,  Arkansas  Much 
aunferous  pynte  has  also  been  mined  in  the  southern  states  and  the 
Rocky  Mountain  region  for  the  gold  it  contains  This  metal  is  sepa- 
rated from  the  pyrite  partly  by  crushing  and  amalgamation  and  partly 
by  smelting  or  by  leaching  processes.  In  the  former  case  the  gold 
occurs  as  inclusions  of  the  metal  in  the  pynte. 


Cobaltite  (CoAsS) 

Cobaltite  is  a  alver-nvhite  or  steel-gray  mineral  occurring  in  massive 
forms  or  in  distinct  crystals  exhibiting  beautifully  their  hemihedral 
character  It  is  completely  isomorphous  with  the  corresponding  nickel 
compound,  gersdorffite  (NiAsS),  and  consequently  mixtures  of  the 
two  are  common 

Cobaltite  usually  contains  some  iron  and  often  a  little  nickel 
Theoretically,  it  consists  of  19  3  per  cent  S,  45  2  per  cent  As  and  35  5 
Co  The  compositions  of  a  massive  variety  from  Siegcn,  Westphalia, 
and  that  of  crystals  from  Nordmark,  Norway,  are  as  follows 

As  S  Co  Fe  Ni          Total 

Siegen  45  31         19  35        33  71         i  63  100  oo 

Nordmark         44  77        20  23        29  17        4  72        i  68        100  57 

The  crystallization  of  cobaltite  is  perfectly  isomorphous  with  that 
of  pyrite,  though  the  number  of  its  forms  observed  is  far  smaller  The 

most  common  planes  are  those  of  oo  0  oo  (100) ,  0(i  1 1 )  and (210) 

The  cleavage  of  cobalt  is  fairly  good  parallel  to  oo  0  oo  (100)  Its 
fracture  is  uneven,  its  hardness  is  5  5  and  its  density  about  6  2  The  color 
of  the  mineral,  as  stated  above,  varies  between  silver-white  and  steel- 
gray  Its  streak  is  grayish  black  It  is  a  good  conductor  of  electricity 

In  the  open  tube  cobaltite  reacts  for  S  and  As  On  charcoal  it 
yields  a  magnetic  globule  which  when  fused  with  borax  on  platinum 
wire  yields  a  deep  blue  bead  It  weathers  fairly  readily  to  the  rose- 
colored  cobalt  arsenate  known  as  erythnte  (Coa(As04)2  SEfeO) 

By  its  crystallization  and  color  cobaltite  is  distinguished  from 
nearly  all  other  minerals  but  those  of  the  same  group  From  most  of 
these  it  is  easily  distinguished  by  its  blowpipe  reactions  foi  sulphur, 
arsenic  and  cobalt 

Occurrence  and  Origin — Cobaltite  occurs  mainly  m  veins  that  are 
believed  to  have  been  filled  by  upward  moving  solutions  emanating 
from  igneous  rocks  It  is  associated  with  compounds  of  nickel  and  other 
cobalt  compounds  and  with  silver  and  copper  ores 

Localities  — Cobaltite  is  not  very  widely  distributed  Large,  hand- 
some crystals  occur  at  Tunaberg  in  Sweden,  at  Nordmark,  Norway, 
at  Siegen,  Westphalia,  and  near  St  Just  in  Cornwall,  England  It  is 
found  also  in  large  quantity  at  Cobalt,  Ontario,  associated  with  silver 
ores  and  nickel  compounds 


Uses — Cobaltite  is  said  to  be  used  b\  jewelers  in  India  in  the  pro- 
duction of  a  blue  enamel  on  gold  ornaments  It  is  employed  also  in  the 
manufacture  of  blue  and  green  pigments  and  in  the  manufacture  of  com- 
pounds used  in  small  quantity  in  the  various  arts  Smalt  is  the  most 
valuable  of  the  cobalt  pigments  and  is  at  present  the  chief  commercial 
compound  of  this  metal  It  is  a  deep  blue  glass  that  cheers  from 
ordinary  glass  in  containing  cobalt  in  place  of  calcium  Smalt  is  made 
from  cobaltite  and  from  other  cobalt  ores  b\  fusion  \\ith  a  mixture  of 
quartz  and  potassium  carbonate  Certain  cobalt  compounds  are  sug- 
gested as  excellent  driers  for  oils  and  varnishes  The  mineral  is  also 
utilized  as  an  ore  of  cobalt,  \\hich  in  the  form  of  stelhte,  an  alloy  com- 
posed of  70  per  cent  cobalt,  15  per  cent  chromium  and  15  per  cent 
molybdenum  or  tungsten,  bids  fair  to  acquire  a  large  use  as  a  material 
for  the  manufacture  of  table  cutlery  and  edged  tools  The  use  of  the 
metal  has  also  been  suggested  as  a  material  for  coinage  in  place  of 

Production — Most  of  the  cobalt  of  commerce  is  handled  by  the 
trade  in  the  form  of  the  oxide  It  is  produced  from  the  \  anous  cobalt 
minerals,  mainly  as  a  by-product  in  the  extraction  of  nickel,  and  hence 
ver>  little  is  obtained  from  ccbaltite  The  mines  at  Cobalt,  however, 
have  furnished  a  large  quantity  of  cobaltite  and  smaltite  \uthin  the  past 
few  years  and  these  have  gone  into  the  manufacture  of  the  oxide,  of 
uhich  about  515  tons  -\\ere  produced  in  1912,  ha\mg  a  \alue  of 

Smaltite  (CoAs>) 

Smaltite  is  another  important  ore  of  cobalt  It  is  found  in  crystals 
and  masses 

Its  theoretical  composition  is  71  88  per  cent  As  and  28  12  per  cent 
Co,  though  it  usually  contains  also  S,  Ni,  Fe  and  frequently  traces  of 
Bi,  Cu  and  Pb  Since  it  is  isomorphous  \uth  the  arsenide  of  nickel 
chloanthite  (NiAs2),  mixed  crystals  of  the  t\\o  are  common  Moreover, 
sharply  defined  crystals  have  been  found  to  consist  of  mechanical  mix- 
tures of  several  compounds 

Smaltite  occurs  in  small  crystals  of  cubical  habit  with  ooOoo  (100), 
0(in)  and  various  pyritoids  predominating 

The  mineral  is  tin-white  to  steel-gray,  and  opaque,  and  has  a  grayish 
black  streak  It  is  often  covered  ^ith  an  iridescent  or  a  gray  tarnish. 
Its  cleavage  is  indistinct,  its  fracture  uneven,  its  hardness  5-6  and 
density  6  3-7  It  is  a  good  electrical  conductor 

Before  tie  blowpipe  on  charcoal  smaltite  yields  arsenic  fumes  and  a 


magnetic  globule  of  metallic  cobalt     It  is  soluble  in  HNOs,  yielding  a 
rose-colored  solution  and  a  precipitate  of  As2Os 

The  mineral  is  fairly  easily  distinguished  from  most  other  minerals 
by  its  color  and  blowpipe  reactions  From  cobaltite  it  is  distinguished  by 
the  lack  of  S  From  a  few  others  that  are  not  described  in  this  volume 
it  can  be  distinguished  by  its  crystallization  or  by  quantitatn  e  analysis 

Synthesis  —  Smaltite  crystals  are  produced  when  hydrogen  acts  at  a 
high  temperature  upon  a  mature  of  the  chlorides  of  cobalt  and  arsenic 

Occurrence  and  Ongm  —Smaltite  is  found  associated  with  cobaltite 
in  nearly  all  of  its  occurrences  It  is  especially  abundant  at  Cobalt,  Out 
As  in  the  case  of  most  other  cobalt  minerals,  its  presence  is  indicated  by 
deposits  of  rose-colored  erythnte  which  coat  its  surfaces  wherever  these 
are  exposed  to  moist  air  Its  methods  of  occurrence,  origin  and  uses 
are  the  same  as  for  cobaltite  (p  107). 

Chloantfaite  (NiAso)  resembles  smaltite  in  most  of  its  characteris- 
tics The  two  minerals  grade  into  each  other  through  isomorphous 
mixtures  Those  mixtures  in  which  the  cobalt  arsenide  is  in  excess 
are  known  as  smaltite,  while  those  in  which  NiAs  predominates  arc 
called  chloanthite  The  pure  chloanthite  molecule  is  Ni=  28  i  per  cent, 
As  =7 1  9  per  cent 

The  two  minerals  can  be  distinguished  when  unmixed  with  one 
another  by  the  blowpipe  reactions  for  Co  and  Ni  In  mixed  ciysUis 
the  predominance  of  one  or  the  other  arsenides  can  be  determined  only 
by  quantitative  analysis 

Chloanthite  containing  much  iron  is  distinguished  as  thathamite, 
from  Chatham,  Conn  ,  where  it  occurs  with  arsenopynte  and  niccohte  in 
a  mica-slate 

The  mode  of  occurrence  of  chloanthite  and  the  localities  at  which 
it  is  found  are  the  same  as  in  the  case  of  smaltite. 

Spenyhte  (PtAs2) 

Sperryhte  is  extremely  rare  It  is  referred  to  here  because  it  is  the 
only  platinum  compound  occurring  as  a  mineral  Chemically,  it  is 
43  S3  Per  cent  As  and  56  47  per  cent  Pt,  but  it  contains  also  small  quan- 
tities of  Sb,  Pd  and  Fe 

Its  crystals  are  simple  They  contain  only  0(iu),  ooOoo(ioo), 
oo  0(no)  and  several  pyntoids  Their  habit  is  usually  octahedral  or 

The  mineral  is  opaque  and  tin-white,  and  its  streak  black  Its  hard- 
ness is  6-7  and  density  10  6 


In  the  closed  glass  tube  it  remains  unchanged,  but  in  the  open  tube 
it  gives  a  sublimate  of  As^Os  When  dropped  upon  red-hot  platinum 
foil  it  immediately  melts,  giving  rise  to  fumes  of  As20s,  and  forming 
blisters  on  the  foil  that  are  not  distinguishable  from  the  original  platinum 
in  color  or  general  character  It  is  shnvh  soluble  in  concentrated  HC1 
and  aqua  regia 

Synthesis  — The  mineral  has  been  produced  by  leading  arsenic  fumes 
over  red-hot  platinum  in  an  atmosphere  of  h\drogen 

Occurrence  and  Localities — Sperrylite  occurs  as  little  crystals  com- 
pletely embedded  in  the  chalcopynte  (CuFeSo)  and  the  gossan  of  a 
nickel  mine,  and  in  the  chalcop\nte  of  a  gold-quartz  vein  near  Sudbury, 
Ontario,  in  covelhte  at  the  Rambler  Mine,  Encampment,  \V\ormng, 
and  as  flakes  in  the  sands  of  streams  in  the  Co\\ee  Valle\ ,  Macon  Co  ,  Ga 
The  flakes  resemble  very  close,!}  native  platinum,  from  which  they  are 
of  course,  easily  distinguished  by  the  test  for  arsenic 

Uses  — The  sperryhte  from  Sudbury  and  \V}  ommg  furnish  much  of 
the  platinum  produced  in  the  United  States  (see  p  64) 


Three  members  of  the  marcasite  group  are  important,  all  are  inter- 
esting from  the  fact  that  they  are  so  alike  in  their  cr\stalhzation  that  a 
description  of  the  forms  belonging  to  any  one  of  them  might  serve  as  a 
description  of  those  belonging  to  all  others  The  crystallization  of  the 
group  is  orthorhombic  (rhombic  bipyramidal  class),  with  an  axial  ratio 
approximately  a  b  '  c=  7  1:12 

Marcasite  (FeS2) 

Marcasite,  the  dimorph  of  pynte,  resembles  this  mineral  so  closely 
that  in  massive  specimens  it  is  difficult  to  distinguish  between  the  two 
They  are  nearly  alike  in  hardness,  in  color  and  in  chemical  properties 
Marcasite  is  a  little  lighter  m  color  than  pynte  Its  density  is  less 
(about  4  9),  and  it  possesses  a  greater  tendency  to  tarnish  on  exposed 

This  tarnish  indicates  that  the  mineral  is  more  susceptible  to  altera- 
tion than  is  pynte  One  of  the  products  of  this  alteration  is  ferrous  sul- 
phate, which  may  often  be  detected  by  its  taste  upon  touching  the  tongue 
to  specimens  of  the  mineral  In  crystallized  specimens  there  is  not  the 
least  difficulty  in  distinguishing  between  them,  suice  their  crystallization 
is  very  different 

Marcasite  is  orthorhombic  (rhombic  bipyramidal  class),  with  the 



axial  ratio  7662  i  i  2342  Its  simple  crystals  often  possess  a  tabular 
or  a  pyramidal  habit  (Figs  44  and  45)  In  the  former  case  oP(ooi)  is 
the  predominant  face,  and  m  the  latter  case  the  two  domes  P  60  (101) 

FIG  44  FIG  45 

FIG  44— Marcasite  Crystal  with  °oP,no(w),  oP,ooi(c),  P^o  ,  on  (/)  and  JPS5 , 

013  (T») 

FIG  45  — Marcasite  Crystal  with  Forms  as  Indicated  in  Fig  44,  and  P  M  ,  101  (e) 

and  P,  in  (s) 

andP  <56  (on)     The  other  forms  observed  on  most  crystals  are  oo  P(iio), 
P(III),  and  often  |P  oo  (013) 

Twins  are  very  common,  with  oo  P(no)  the  twinning  plane  (Fig  46) 
Sometimes  these  are  aggregated  by  repeated  twinning  into  serrated 
groups  known  as  cockscomb  twins  or  spearhead  twins  (Fig  47),  because 

FIG  46  FIG  47 

FIG  46  —Twin  of  Marcasite  about  oo  P(iio) 

FIG  47 — Spearhead  Group  of  Marcasite     Fourling  Twinned  about  no  and  then 

about  i  To 

of  the  outlines  of  their  edges.    In  many  instances  the  crystals  aie  acic- 
ular  or  columnar  in  habit,  forming  radiating  groups  with  globular,  rem- 
form  and  stalactitic  shapes      Concretions  are  also  common     The  basal 
plane  is  usually  striated  parallel  to  the  edge  between  it  and  P  oo  (on) 
The  cleavage  is  distinct  parallel  to  oo  P(iio)     The  fracture  is  uneven 


When  powdered  marcasite  is  treated  \\ith  cold  nitric  acid  and 
allowed  to  stand,  it  decomposes  \uth  the  separation  of  sulphur 

Marcasite  readih  alters  to  limonite  The  fact  that  pyrite,  sphaler- 
ite, chalcopyrite,  and  other  minerals  form  pseudomorphs  after  it 
indicates  that,  under  suitable  conditions,  it  alters  also  to  these  com- 
pounds The  mineral  is  in  most  cases  a  direct  result  of  precipitation 
from  hot  solutions 

Synthesis  — Marcasite  crystals  ha\e  been  prepared  by  the  reduction 
of  FeSQi  by  charcoal  in  an  atmosphere  of  EfeS 

Occurrence  ani  Uses  — The  mineral,  like  pyrite,  is  found  embedded 
in  rocks  in  the  form  of  crystals  and  concretions,  and  also  as  the 
gangue  masses  of  veins  It  constitutes  nearly  the  entire  filling  of  some 
veins,  and  forms  druses  on  the  walls  of  cavities  in  both  rocks  and  miner- 
als It  also  replaces  the  organic  matter  of  fossils  preserving  their  shapes 
— thus  producing  true  pseudomorphs 

When  associated  \\ith  pyrite  it  is  mined  together  \\ith  this  mineral 
as  a  source  of  sulphur 

Localities — Crystalline  marcasite  occurs  m  such  great  quantity 
near  Carlsbad  m  Bohemia  that  it  is  mined  The  cockscomb  variety  is 
found  in  Derbyshire,  England,  and  crystals  at  Schemmtz  in  Hungary 
and  at  Andreasberg  and  other  places  in  the  Harz  In  the  United  States 
the  mineral  occurs  as  crystals  at  a  great  number  of  places,  being  par- 
ticularly abundant  m  the  lead  and  zinc  localities  of  the  Mississippi 
Valley,  where  it  sometimes  forms  stalactites  The  stalactites  from 
Galena,  111 ,  often  consist  of  concentric  layers  of  sphalerite,  galena  and 
crystallized  marcasite 

Arsenopyrite  (FeAsS) 

Arsenopyrite,  or  mispickel,  is  the  most  important  ore  of  arsenic 
It  is  found  in  crystals  and  in  compact  and  granular  masses.  It  is  a 
silver-white  metallic  mineral  resembling  very  closely  cobaltite  in  its 
general  appearance 

The  formula  FeAsS  for  arsenopynte  is  based  on  analyses  like  the 

As          S          Fe       Total 

Specimen  from  Hohenstein,  Saxony         45  62    19  76    34  64    100  02 
Specimen  from  Mte  Chalanches,  France  45  78    ig  56    34  64      99  98 

Theoretically,  the  mineral  consists  of  its  components  m  the  following 
proportions,  As  46  per  cent,  S  19  7  per  cent,  Fe  34  3  per  cent  In  many 
specimens  the  iron  is  replaced  in  part  by  cobalt,  nickel  or  manganese. 



Sometimes  the  cobalt  is  present  in  such  large  quantity  that  the  mineral 
is  smelted  as  an  ore  of  this  metal 

The  axial  ratio  of  arsenopynte  is  6773  i  i  1882  Its  crystals  are 
usually  simpler  than  those  of  marcasite  (Fig  48),  though  the  number  of 
planes  observed  in  the  species  is  larger.  Most  of  the  untwmned  crystals 

are  a  combination  of  oo  P(no) 
with  JP66  (014),  or  P  06  (on), 
or  POO(IOI),  and  have  a  pris- 
matic habit.  Twins  are  not 
rare  The  twinning  plane  is 
the  same  as  in  marcasite, 
and  repetition  is  often  met 
with  The  angle  no/\i"io= 
68°  13' 

FIG   48-Arsenopynte  Crystals    with   cop,        The  brachydomes  are  stri- 
no  (m) ,  iP  oo ,  014  (M),  and  P  5 ,  on  (j)       ated   horizontally,  and    often 

the  planes  ooP(no)  are  stri- 
ated parallel  to  the  edge  oo  P(no)  A?  *>  (101) 

The  cleavage  of  arsenopynte  is  quite  perfect  parallel  to  ooP(no) 
The  mineral  is  brittle  and  its  fracture  uneven  Its  hardness  is  5  5-6 
and  density  about  6  2  Its  color  is  silver-white  to  steel-gray,  its  streak 
grayish  black  It  is  a  good  conductor  of  electricity 

In  the  closed  tube  arsenopynte  at  first  gives  a  red  sublimate  of  AsS 
and  then  a  black  mirror  of  arsenic  On  charcoal  it  gives  the  usual 
reactions  for  sulphur  and  arsenic  Cobaltiferous  varieties  react  for 
cobalt  with  borax.  The  mineral  yields  sparks  when  struck  wilh.  steel 
and  emits  an  arsenic  smell  It  dissolves  m  nitric  acid  with  the  separa- 
tion of  sulphur 

Arsenopynte  is  distinguished  from  the  cobalt  sulphides  and  arsenides 
by  the  absence  of  Co 

Synthesis — Crystals  of  the  mineral  are  produced  by  heating  in  a 
closed  tube  at  300°  precipitated  FeAsS  in  a  solution  of  NaHCO* 

Occurrence — Arsenopynte  crystals  are  often  found  disseminated 
through  crystalline  rocks,  and  often  embedded  m  the  gangue  minerals  of 
veins  Like  pyrite  and  marcasite  they  frequently  fill  vein  fissures.  Its 
associates  are  silver,  tin  and  lead  ores,  chalcopyrite,  pynte  and  sphalerite 
Localities — The  mineral  is  abundant  at  Freiberg,  m  Saxony,  at 
Tunaberg,  in  Sweden,  and  at  Inquisivi  Mt ,  Sorato,  m  Bolivia 

It  also  occurs  in  fine  crystals  at  Francoma  in  New  Hampshire,  at 
Blue  Hill  m  Maine,  at  Chatham  in  Connecticut,  and  at  St.  Francois, 
Beauce  Co,  Quebec  Massive  arsenopynte  is  found  near  Kecscville 


Essex  Co  ,  near  Edenville,  Orange  Co  ,  and  near  Carmel,  Putnam  Co , 
N  Y  ,  and  at  Re\\ald,  Flo\d  Co  ,  Va  In  most  cases  it  is  appaiently 
a  result  of  pneumatoh  sis 

Uses  — Arsenopynte  was  formerly  the  source  of  nearly  all  the  arsenic 
of  commerce  The  mineral  is  concentrated  b\  mechanical  methods,  and 
the  concentrates  are  heated  in  retorts,  when  the  following  reaction  takes 
place  FeAsS  =  FeS+As  The  arsenic  being  volatile  is  conducted 
into  condensing  chambers  where  it  is  collected  When  the  mineral  con- 
tains a  reasonable  amount  of  cobalt  or  of  gold  these  metals  are  extracted 

Uses  of  Arsenic — The  metal  arsenic  has  \ery  little  use  in  the  arts, 
though  its  compounds  find  many  applications  as  insecticides,  medicines, 
pigments,  in  tanning,  etc  The  basis  of  most  of  these  is  AsoOs,  and 
this  is  produced  directly  from  the  fumes  of  smelters  working  on  arsenical 
gold,  silver  and  copper  ores  Only  a  portion  of  such  fumes  are  saved, 
however,  as  even  half  of  those  produced  at  a  single  smelter  center 
(Butte,  Montana),  would  more  than  supply  the  entire  demand  of  the 
United  States  for  arsenic  and  its  compounds  Under  these  conditions 
the  mining  of  arsenical  pynte  as  a  source  of  arsenic  has  ceased  so  far 
as  the  United  States  is  concerned 

Lollingite  (FeAso)  is  usually  massive,  though  its  rare  crystals  are 
isomorphous  in  e\ery  respect  with  those  of  arsenopynte  The  pure 
mineral  is  not  common  Most  specimens  are  mixtures  of  lollmgite  with 
arsenopynte  or  other  sulphides  or  arsenides. 

The  mineral  is  silver-white  or  steel-gray  Its  streak  is  grayish  black 
Its  hardness  is  5-5  5  and  density  about  72  It  readily  fuses  to  a  mag- 
netic globule,  at  the  same  time  evolving  arsenic  fumes  It  is  soluble  in 

It  usually  occurs  in  veins  associated  with  other  sulphides  and  arsen- 
ides It  is  found  at  Pans,  Maine;  at  Edenville  and  Monroe,  N.  Y.; 
at  vanous  mines  in  North  Carolina,  and  on  Brush  Creek,  Gunnison 
Co.,  Colo  At  the  last-named  locality  the  mineral  is  in  star-shaped 
crystalline  aggregates,  in  twins  and  trillings,  associated  with  siderite 
and  barite. 


The  sylvanite  group  includes  at  least  three  distinct  minerals,  all  of 
which  are  ditellurides  of  gold  or  silver.  The  group  is  isodunorphous. 
The  pure  gold  tellunde  is  known  only  in  monochmc  crystals,  but  the 
isomorphous  mixtures  of  the  gold  and  silver  compounds  occur  both  in 
monochmc  and  orthorhombic  crystals 


Orthorhombic  bipyramidal  Monoclmic  prismatic 

AuTeo  Calavente 

Krennente  (Ag  Au)Te2  Syhamte 

All  three  minerals  are  utilized  as  ores  of  gold  While  occurring  only 
in  a  few  places,  they  are  sufficiently  abundant  at  some  to  be  mined 

Calaverite  (AuTe2) 

Calavente  is  a  nearly  pure  gold  chloride  However,  it  is  usually 
intermixed  with  small  quantities  of  the  silver  tellunde  An  analysis  of  a 
specimen  from  Kalgoorhe,  Australia,  gave  Te=5727,  Au=4i  37, 


Calaverite  crystallizes  m  the  monoclmic  system  (prismatic  class)  in 
crystals  that  are  elongated  parallel  to  the  orthoaxis  and  deeply  striated 
in  this  direction.     Their  axial  ratio  is  i  6313     i  '  i  1449  with  £=90°  13' 
The   prominent    forms   are    ooP  66(100),    ooP«D(oio),  oP(ooi), 
-Poc(ioi),    +P6o(ioT),    -2Poo(20i),    +2P66(2oT),  and   P(in) 
Twinnmg  is  common  and  the  resulting  tuiins  are  very  complicated 
Usually,  however,  the  mineral  occurs  massive  and  granular 

Calavente  is  opaque,  silver-white  or  bronzy  yellow  in  color  and  has  a 
yellow-gray  or  greenish  gray  streak.  Its  surface  is  frequently  covered 
with  a  yellow  tarnish.  The  mineral  is  brittle  and  without  distinct  cleav- 
age Its  hardness  is  2-3  and  density  9  04 

On  charcoal  before  the  blowpipe  the  mineral  fuses  easily  to  a  yellow 
globule  of  gold,  yielding  at  the  same  tune  the  fumes  of  tellurium  oxide. 
It  dissolves  in  concentrated  EfeSO.*,  producing  a  deep  red  solution.  When 
treated  with  HNOs  it  decomposes,  leaving  a  rusty  mass  of  spongy  gold 
The  solution  treated  with  HC1  usually  yields  a  slight  precipitate  of  silver 

Calaverite  is  distinguished  from  most  other  minerals  by  the  test  for 
tellurium  It  is  distinguished  from  fetzite  (p  80),  by  its  crystallization 
and  the  fact  that  it  gives  a  yellow  globule  when  roasted  on  charcoal, 
and  from  sylvamte  by  the  small  amount  of  silver  it  contains,  its  higher 
specific  gravity,  its  color  and  its  lack  of  cleavage  It  is  distinguished 
from  krennente  by  its  crystallization 

Occurrence  — The  mineral  occurs  in  veins  with  the  other  tellurides 
associated  with  gold  ores  in  Calaveras  Co ,  Cal ,  and  at  the  localities 
mentioned  for  petzite  (see  p  81)  It  is  believed  to  have  been  deposited 
by  pneumatolytic  processes  or  by  ascending  magmatic  water  at  com- 
paratively low  temperatures. 


Uses. — The  mineral  is  mined  with  other  tellundes  in  Boulder  Co , 
and  at  Cripple  Creek,  Colorado,  as  an  ore  of  gold 

Sylvamte  (Ag  Au)Te2 

Sylvamte  is  more  common  than  calavente  It  is  an  isomorphous 
mixture  of  gold  and  silver  tellundes  in  the  ratio  of  about  i  .  i  Analyses 

I    Te=62  16  Au=24  45  Ag=i3  39         Total=ioo  oo 

II    Te=59  78  Au=26  36  Ag  =  i3  86  "       ico  oo 

III    Te=58  91  Au=29  35  Ag=n  74  k*       100  oo 

I   Theoretical  for  AgTe2+  \uTe2 
II  and  III   Specimens  trom  Boulder  Co  ,  Colo 

In  crystallization  the  mineral  is  isomorphous  with  calavente,  with 
an  axial  ratio  a  b  .  c=  i  6339  i  :  i  1265  and  $=90°  25'  Its  crystals 
are  usually  rich  in  planes,  about  75  ha\mg  been  identified  Their  habit 
is  usually  tabular  parallel  to  ooP  ob  (GIO),  with  this  plane,  —P  5c  (101), 
oP(ooi),  oo  P  5b  (100)  and  2P2(T2i)  predominating  The  mineral  also 
occurs  in  skeleton  crystals  and  in  aggregates  that  are  platy  or  granular 
Twinning  is  common,  \\ith  — P<X(IOI)  the  twinning  plane  Many 
twinned  aggregates  form  networks  suggesting  writing,  hence  the  name 
"  Schnfterz  ''  often  applied  to  the  mineral  by  the  Germans 

Sylvamte  is  silver-white  or  steel-gray  and  has  a  brilliant  metallic 
luster  and  a  silver-white  or  yellowish  gray  streak  Its  hardness  is 
between  i  and  2  and  its  densiU  7  9-8  3  Moreover,  it  possesses  a  per- 
fect cleavage  parallel  to  oo  P  ob  (oio) 

Its  chemical  properties  are  the  same  as  those  of  calavente,  but  the 
silver  precipitate  produced  by  adding  HC1  to  its  solution  m  HNOs  is 
always  large  It  is  best  distinguished  from  the  gold  tellunde  by  its 
cleavage  and  from  fetzite  ((AgAu^Te)  and  lessite  (AgsTe)  by  its 
crystallization,  and  by  the  yellow  metallic  globule  produced  when  the 
mineral  is  roasted  on  charcoal  It  is  distinguishable  from  krennente  by 
its  crystallization 

Localities  and  Origin  — Sylvanite  occurs  with  the  other  tellundes  in 
veins  at  Offenbanya  and  Nagyag  in  Transylvania,  at  Cripple  Creek  and 
m  Boulder  Co  ,  Colo  ,  near  Kalgoorhe,  W  Australia,  in  small  quan- 
tities near  Balmoral  in  the  Black  Hills,  S  D  ,  and  at  Moss,  near  Thunder 
Bay,  Ontano  Like  calavente  it  TV  as  deposited  by  magmatic  water,  or 
by  hot  vapors 

Uses  — It  is  mined  with  calaverite  as  a  gold  and  silver  ore  at  Cripple 
Creek  and  in  Boulder  Co ,  Colo. 


THE  sulpho-salts  are  salts  of  acids  analogous  to  arsenic  acid, 
and  arsenious  acid,  HsAsOs,  and  the  corresponding  antimony  acids 
HsSb04  and  EfeSbOs  The  sulpho-acids  differ  from  the  arsenic  and  the 
antimony  acids  in  containing  sulphur  in  place  of  oxygen,  thus  HsAsS-i, 
HsAsSa,  H3SbS4  and  H3SbS3.  The  mineral  enargite  may  be  regarded  as 
a  salt  of  sulpharsenic  acid,  thus  CusAsS-i,  copper  having  replaced  the 
hydrogen  of  the  acid  Proustite,  on  the  other  hand,  is  AgsAsSs,  or  a 
salt  of  sulpharsemous  acid.  The  salts  of  sulpharsenic  acid  are  called 
sulpharsenates,  while  those  derived  from  sulpharsemous  acid  are  known 
as  sulpharsemtes  The  sulpharsenates  are  not  represented  among  the 
commoner  minerals,  although  the  copper  salt  enargite  is  abundant  at  a 
few  places  A  number  of  salts  of  other  sulphur-arsenic  acids  are  known 
but  they  are  comparatively  rare 

There  is  another  class  of  compounds  with  compositions  analogous 
to  those  of  the  sulpho-salts,  though  their  chemical  nature  is  not  well 
understood  This  is  the  group  of  the  sulpho-ferntes  We  know  that 
certain  hydro-sides  of  iron  may  act  as  acids  under  certain  conditions 
The  sulpho-ferrites  may  be  looked  upon  as  salts  of  these  acids  in  which, 
however,  the  oxygen  has  been  replaced  by  sulphur,  as  in  the  case  of  the 
sulpho-acids  referred  to  above  Thus  by  replacement  of  0  by  S,  m 
feme  hydroxide  Fe(OH)s  the  compound  Fe(SH)s  or  HsFeSs  results 
The  salts  of  this  acid  are  sulpho-ferrites  This  acid,  by  loss  of  HaS, 
may  give  rise  to  other  acids  in  the  same  way  that  sulphuric  acid  (EfeSO/O, 
by  loss  of  HaO,  gives  nse  to  pyrosulphuric  acid  In  the  case  of  the 
sulpho-acid  we  may  have  HsFeSs— H2S=HFeS2  The  copper  salt  of 
this  acid  is  the  common  mineral  chalcopyrite,  CuFeS2 

The  sulpho-salts  are  very  numerous,  but  only  a  few  of  them  are  of 
sufficient  importance  to  warrant  a  description  in  this  book 




The  sulpharsemtes  and  sulphantimomtes  are  denvatives  of  the 
ortho  acids  HsAsSs  and 


The  ortho  salts  are  compounds  in  \\hich  the  hydrogen  of  the  ortho 
acids  is  replaced  by  metals  They  include  a  large  number  of  minerals, 
of  which  the  following  are  the  most  important. 

Boitrnomte    (Cus  Pb)s  (SbSs)2  Orthorhombic 

Pyrargynte  AgsSbSa  Hexagonal 

Proustite       AgsAsSs  Hexagonal 

Pyrargynte  (AgsSbSs) 

Pyrargyrite,  or  dark  ruby  silver,  is  an  important  silver  ore,  especially 
in  Mexico,  Chile  and  the  \\estern  United  States.  The  name  ruby  silver 
is  given  to  it  because  thin  splinters  transmit  deep  red  light  The  mineral 
is  usually  mixed  with  other  ores  in  compact  masses,  but  it  also  forms 
handsome  crystals 

The  composition  of  pyrargyrite  is  represented  by  the  formula  AggSbSs 
which  demands  17  82  per  cent  S  ,  22  21  per  cent  Sb  ,  59  97  per  cent  Ag 
Many  specimens  contain  also  a  small  quantity  of  arsenic,  through  the 
admixture  of  the  isomorphous  compound  proustite  The  analyses  given 
below  show  the  effect  of  the  intermixture  of  the  two  molecules 

S             Sb  As           Ag  Total 

Andreasberg,  Harz  17  65  22  36  59  73  99  77 

Zacatecas,  Mexico           17  74  22  39  27  60  04  100  44 

Freiberg,  Saxony              17  95  18  58  2  62  60  63  99  78 

The  crystals  of  pyrargyrite  are  rhombohedral  and  hemunorphic 
(ditngonal  pyramidal  class),  with  an  axial  ratio  i  :  8038  They  are 
usually  quite  complex  and  are  often  twinned.  The  species  is  very  rich 
in  forms,  not  less  than  150  having  been  reported  The  most  prominent 
of  these  are  ooP2(ii2o),  ooP(ioTo),  R(ioli),  -iR(oil2)  and  the 
scalenohedrons  R3(2i3i)  and  iR3(2i34)  (Fig  ^49)  In  the  commonest 
twinning  law  the  twinning  plane  is  ooP2(ii2o)  and  the  composition 


face  oPfooi)  The  c  axes  in  the  twinned  portions  are  parallel  and  the 
o=P2(ii2~o)  planes  coincident,  so  that  the  t\\m  at  a  hasty  glance  looks 
like  a  simple  crystal  The  angle  roll  /\lioi  =  71°  22' 

The  cleavage  of  pyrargynte  is  distinct  parallel  to  R(ioTi)  Its  frac- 
ture is  conchoidal  or  une\  en  The  mineral  is  apparently  opaque  and  its 
color  is  grayish  black  in  reflected  light,  but  is  trans- 
parent or  translucent  and  deep  red  in  transmitted 
light  Its  streak  is  purplish  red  For  lithium 
light  03=3084,  €=2881  It  is  not  an  electrical 

In  the  closed  tube  the  mineral  fuses  easily  and 


ghes  a   reddish   sublimate      When  heated 

^  sodium  carbonate  on  charcoal  it  is  reduced  to  a 

P\ra^g\nte  *  with  g^°bule  of   silver,  \vhich,  when   dissolved  in  nitric 

1 1 20    (a)  acid,   yields    a   silver    chloride   precipitate  when 

I  treated  \\ith  a  soluble  chloride     The  mineral  dis- 

solves  in  nitric  acid  with  the  separation  of  sulphur 
and  a  white  precipitate  of  antimony  oxide  It  is  also  soluble  in  a 
strong  solution  of  KOH  From  this  solution  HC1  precipitates  orange 
Sb2Ss  (compare  proustite) 

The  color  and  streak  of  p>rargynte,  together  with  its  translucency, 
distinguish  it  from  nearly  all  other  minerals  Its  reaction  for  silver 
serves  to  distinguish  it  from  cuprite,  dnnalar  and  realgar,  which  it  some- 
times resembles  The  distinction  between  this  mineral  and  its  iso- 
morph,  proustite,  is  based  on  the  streak  and  the  reaction  for  anti- 

Pyrargynte  occurs  as  a  pseudomorph  after  native  silver.  On  the 
other  hand  it  is  occasionally  altered  to  pynte  or  argentite,  and  some- 
times to  silver 

Syntheses  —  Microscopic  crystals  ha\e  been  made  by  heating  in  a 
porcelain  tube,  metallic  silver  and  antimony  chlorides  in  a  current  of 
IfeS,  and  by  the  action  of  the  same  gas  at  a  red  heat  on  a  mixture  of 
metallic  silver  and  melted  antimony*  o\ide 

Occurrence,  Localities  and  Origin  —  Pyrargynte  occurs  in  veins  asso- 
ciated with  other  compounds  of  silver  and  scmetimes  with  galena  and 
arsenic  It  is  most  common  in  the  zone  of  secondary  enrichment  of 
silver  veins.  The  crystallized  variety  is  found  at  Andreasberg  in  the 
Harz,  at  Freiberg,  in  Saxony,  at  Pnbram,  in  Bohemia,  at  many  places 
in  Hungary,  and  at  Chanarcillo,  in  Chile  The  massive  variety  is  worked 
as  an  ore  of  silver  at  Guanajuato  in  Mexico  and  in  several  of  the  western 
states,  as,  for  instance  in  the  Ruby  district,  Gunmson  Co  ,  and  in  other 


mining  districts  m  Colorado,  near  Washoe  and  Austin,  Nevada,  and  at 
several  points  in  Idaho,  Ne\v  Mexico,  Utah  and  Arizona 

Uses  — The  mineral  is  an  important  ore  of  silver  in  Mexico  and  in 
the  western  United  States  It  is  usually  associated  with  other  sulphur- 
bearing  ores  of  sil\er,  the  metal  being  extracted  from  the  mixture  by 
the  processes  referred  to  under  argentite, 

Proustite  (AgsAsSs) 

Proustite,  or  light  ruby  siher,  is  isomorphous  with  p\rargynte  It 
differs  from  the  latter  mineral  in  containing  arsenic  m  place  of  antimony 
It  occurs  both  massive  and  in  crystals,  and  like  pyrargynte  is  an  ore  of 

The  formula  abo\e  given  demands  19  43  per  cent  S,  15  17  per  cent 
As,  and  65  40  per  cent  sih  er  The  analysis  of  a  specimen  from  Mexico 
yields  figures  that  correspond  \ery  nearly  to  these  Cr}stals  from 
Chanarcillo  contain  a  slight  admixture  of  the  antimony  compound 

S  As  Sb  Ag         Total 

Mexico  19  52        14  98  65  39        99  89 

Chanarcillo,  Chile  19  64        13  85        i  41        65  06        99  96 

Like  pyrargynte,  proustite  is  rhombohedral  Its  crystals  are  pris- 
matic or  acute  rhombohedral  The  forms  present  on  them  are  much 
less  numerous  than  those  on  the  corresponding 
antimony  compound,  the  predominant  ones  being 
ocp2(ii2o),  iR(ioT4),  -iR(oil2),  Rd(2i3i), 
~|R4(3557J  and  other  scalenohedrons  (see  Fig 
50)  Twins  are  common,  the  t winning  planes 
being  (i),  parallel  to  JR(iol4)  and  (2)  parallel  to 
R(ioTi)  The  angle  io7i  Alici  =  7i°  12'.  FlG  So-Crystal  of 

The  cleavage,  fracture  and  haidness  of  prous-  JJJHJ  ^  *  Jj 
tite  are  the  same  as  for  pyrargynte  Its  hard-  (j/)  and -|R,  0112  («). 
ness  is  2  and  its  density  is  about  5.6  The  mineral 
is  transparent  or  translucent  Its  color  is  grayish  black  by  reflected 
light  and  scarlet  m  transparent  pieces  by  transmitted  light.  Under  the 
long-continued  influence  of  daylight  the  color  deepens  until  it  becomes 
darker  than  that  of  pyrargynte  Its  streak  is  cirnabar-red  to  brownish 
black  Its  luster  is  adamantine.  It  is  a  nonconductor  of  electncity 
For  sodium  light  03=3  0877,  €=  2  7924 

In  the  closed  tube  proustite  fuses  easily  and  gives  a  slight  sublimate 


of  \\hite  arsenic  oxide     In  its  other  chemical  properties  it  resembles 
pyrargyrite  except  that  it  gi\es  reactions  for  arsenic  \\here  this  mineral 
reacts  for  antimony,  and  yields  onh  sulphur  \\hen  dissohed  in  HNOa 
From  its  solution  in  KOH  a  yellow  precipitate  of  As^Ss  is  thrown  do\\n 
upon  the  addition  of  HC1  (compare  pyrargyrite) 

Proustite  differs  from  pyra  g \nte  in  Us  color,  transparency  and 
streak,  as  \vell  as  in  its  arsenic  reactions  It  is  distinguished  from 
cinnabar  and  cuprite  (CuO)  b>  the  arsenic  test 

Syntheses — Crystals  of  proustite  ha\e  been  produced  by  reactions 
analogous  to  those  that  yield  p\rargynte,  when  arsenic  compounds  are 
employed  in  place  of  antimon\  compounds 

Occurrence  — The  mineral  occurs  under  the  same  conditions  and  with 
the  same  associates  as  pyrargyrite  and  it  yields  the  same  alteration 
products  as  pyrargynte 

Localities  and  Uses — Handsome  crystals  of  proustite  occur  at 
Freiberg  and  other  places  in  Saxony,  at  Wolfach  in  Baden,  at  Markirchen 
in  Alsace  and  at  Chanarcillo  in  Chile  It  is  associated  with  pyrargyrite 
and  with  other  ores  of  silver 

In  the  western  United  States  it  is  quite  abundant,  more  particular!} 
in  the  Ruby  district,  Colorado,  at  Poorman  lode  in  Idaho,  and  in  all  other 
localities  where  pyrargynte  occurs  In  many  it  is  mined  as  an  ore  of 

Bournonite  ((Pb  Cu2)3(SbS3)2) 

Bournomte  is  a  comparatively  rare  mineral  It  occurs  either  in 
compact  or  granular  masses  or  in  well  developed  crystals  of  a  steel 
gray  color  It  is  not  of  any  economic  importance  except  as  it  may  be 
mixed  with  other  copper  compounds  exploited  for  copper 

Analyses  of  bournomte  from  two  localities  are  given  below 

S  Sb 

I-  19  36        23  57 
n.  19  78        23  80 

I  Liskeard,  Cornwall,  England 
II  Felsobinya,  Hungary 

These  analyses  are  by  no  means  accurate,  but  they  show  the  compo- 
sition of  the  mineral  to  be  approximately  Pb,  Cu,  Sb  and  S,  in  which  the 
elements  are  combined  in  the  following  proportions  8=19  8  per  cent, 
Sb=24  7  per  cent,  Pb  42  5  per  cent,  Cu  13  per  cent 

Bournonite  crystals  are  orthorhombic  (rhombic  bipyramidal  class), 







4i  95 

13  27 


99  30 


42  07 

12    82 


98  67 



with  a  .  b  c=  9380  i  8969  They  are  usually  tabular  'Fig  51;,  or 
short,  prismatic  in  habit,  and  are  often  in  repeated  twins  fFig  52*,  with 
wheel-shaped  or  cross-like  forms  The  principal  planes  observed  on 
them  are  oP(ooi),P<^(ioij,  POD  (011  ),iP(ii2),  wP(noi,  xPxiioo, 
and  oo  P  oc  (oio),  though  90  or  more  planes  are  kno\\  n  The  most  com- 
mon twinning  plane  is  oo  P(no)  Angle  IIOAIIO—  86°  20' 

The  luster  of  the  mineral  is  brilliant  metallic  Its  cclcr  and  streak 
are  steel-gray  Its  cleavage  is  imperfect,  parallel  to  QC  P  c£  f  oio;  and  its 
fracture  conchoidal  or  uneven  Its  hardness  is  2  5-3  and  density  5  8 
Like  most  other  metallic  minerals  it  is  opaque  It  is  a  \  ery  poor  con- 
ductor of  electricity 

In  the  closed  tube  bournomte  decrepitates  and  yields  a  dark  red  sub- 
limate In  the  open  tube,  and  on  charcoal,  it  gives  reactions  for  Sb,  S, 
Pb  and  Cu  When  treated  with  nitric  acid  it  decomposes,  producing  a 

FIG  51  FIG  s- 

FIG  51  — Bournomte  Crystal  \uth  oP  ooi  (c],  P  55  ,  101  (0),  \P  112  fu)  and  P  x, 

on  in) 

FIG  52 — Bournonite  Fourlmg  Tuinned  about  x  P,  no  (m)     Form  c  same  as  in 
Fig  51      b  =  =c  P  oo  (oio;  and  a  *=  oc  P  55  s  100) 

blue  solution  of  copper  nitrate  that  turns  to  an  intense  azure  blue  when 
an  excess  of  ammonia  is  added  In  this  solution  is  a  residue  of  sulphur 
and  a  white  precipitate  that  contains  lead  and  antimon\ . 

Bournomte  is  distinguished  from  most  other  minerals  by  its  reactions 
for  both  antimony  and  sulphur.  From  other  sulphantunonites  it  is 
distinguished  by  its  color,  hardness  and  density. 

On  long  exposure  to  the  atmosphere  bournomte  alters  to  the  car- 
bonates of  lead  (cerussitej  and  copper  (malachite  and  azunte) 

Synthesis  — Crystals  of  bournomte  have  been  obtained  by  the  action 
of  gaseous  HkS  on  the  chlorides  and  oxides  of  Pb,  Cu  and  Sb,  at  moderate 

Occurrence — The  mineral  occurs  principally  in  veins  with  galena, 
sphalerite,  stibmte,  chalcopynte  and  tetrahednte 

Localities. — Good  crystals  are  found  in  the  mines  at  Neudorf,  Harz; 
at  Pnbram,  m  Bohemia,  at  Felsobanya,  Kapnik  and  other  places 
in  Hungary,  and  at  various  places  in  Chile.  In  North  America  it  has 


been  found  at  the  Boggs  Mine  in  Yavapai  Co ,  Ariz ,  in  Montgomery 
Co  ,  Ark ,  and  at  Marmora,  Hastings  Co  ,  and  Darling,  Lanark  Co  , 


A  large  number  of  sulpho-salts  are  apparent!}  salts  of  acids  that 
contain  two  or  more  atoms  of  As  or  Sb  in  the  molecule  These  acids 
may  be  regarded  as  derived  from  the  ortho  aads  by  the  abstraction  of 
HsS,  thus  The  arsemous  acid  containing  two  atoms  of  As  may  be 
thought  of  as  2H3AsS3-H2S=H4As2S5  Acids  with  larger  proportions 
of  arsenic  may  be  regarded  as  derived  in  a  similar  manner  from  three  or 
more  molecules  of  the  ortho  acid  Only  a  few  of  these  salts  are  common 
as  minerals.  Among  the  more  common  are  two  that  are  lead  salts  of 
derivatives  of  sulpharsemous  and  sulphantimonous  acids, 

Jamesomte  (PbsSbgSs)  and  Dufrenoysite  (Pb2AsgS5) 

Jamesonite  and  dufrenoysite  are  lead  salts  of  the  acids  H4Sb2Ss  and 
H4As2Ss  Both  minerals  occur  in  acicular  and  columnar  orthorhombic 
crystals  and  in  fibrous  and  compact  masses  of  lead-gray  color  Their 
cleavage  is  parallel  to  the  base  The  minerals  are  brittle  and  have  an 
uneven  to  conchoidal  fracture  Their  hardness  is  2-3  and  density 
5  5-6  The  streak  of  jamesomte  is  grayish  black,  and  of  dufreynosite 
reddish  brown.  Both  minerals  are  easily  fusible  They  are  soluble  in 
HC1  with  the  evolution  of  EfeS,  giving  a  solution  from  which  acicular 
crystals  of  PbCfe  separate  on  cooling  They  are  decomposed  by  HNOs, 
with  the  separation  of  a  white  basic  lead  salt  They  are  found  in  veins 
with  antimony  and  sulphide  ores  abroad  and  at  several  points  in  Nevada 
and  in  the  antimony  mines  in  Sevier  Co ,  Arkansas 


The  sulpharsenates  are  salts  of  sulpharsenic  acid,  HaAsS^  and  the 
sulphantimonates,  the  salts  of  the  corresponding  antimony  acid,  HsSbS^ 
These  compounds  are  much  less  numerous  among  the  minerals  than  the 
sulpharsenites  and  sulphantimomtes.  Moreover,  no  member  of  the 
former  groups  is  as  common  as  several  of  the  members  of  the  latter 
The  most  important  member  is  the  mineral  enargite  (CusAsS^  an  ortho- 
sulpharsenate,  which  in  a  few  places  is  wrought  as  a  copper  ore. 



Enargite,  though  a  rare  mineral,  is  so  abundant  at  a  few  points  that 
it  has  been  mined  as  an  ore  of  copper 

Theoretically,  the  mineral  is  8=326,  As=i9i,  01=483  Most 
specimens,  however,  contain  an  admixture  of  the  isomorphous  anti- 
mony compound,  jamaiimte^  and  consequently  sho\v  the  presence  of 
antimony.  A  specimen  from  the  Rarus  Mine,  Butte,  Montana,  yielded 

S  As  Sb  Cu  Fe         Zn       Ins        Total 

31  44        17  91        i  76        48  67        .33          10         ii        100  32 

The  mineral  crystallizes  in  the  orthorhombic  system  (bipyramidal 
class),  m  crystals  with  an  axial  ratio   8694  :  i :  8308     Their  habit  is 
usually  prismatic,  and  they  are  strongly  striated 
vertically.    The  crystals  are  usually  highly  modi- 
fied, with   the    following  forms  predominating 
oo  P  06(100),   ooP(no),    ooP3(i2o),    ooP^f^o), 
oo  P  06  (oio),  and  oP(ooi)  (Fig  53)     Stellar  trill- 
ings,  with  ooP2(i2o)  the  twinning  plane,  have  a 
pseudohexagonal  habit.    The  mineral  occurs  also 

in  columnar  and  platy  masses  FIG  ^  _Enarglte  Crys_ 

Enargite  possesses  a  perfect  prismatic  cleavage  tal  wth  M  Pj  1IO  (m^ 
and  an  uneven  fracture.  It  is  opaque  with  a  OOP  55,100  (a),  «>pr, 
grayish  black  color  and  streak.  Its  hardness  is  3  i2o(A)andoP,oor(c). 
and  density  44.  It  is  a  poor  electrical  conductor. 

It  is  easily  fusible  before  the  blowpipe  When  roasted  on  charcoal 
it  gives  the  reactions  for  S  and  As,  and  the  roasted  residue  when 
moistened  with  HC1  imparts  to  the  flame  the  azure-blue  color  char- 
acteristic of  copper.  In  the  closed  tube  it  decrepitates  and  gives  a 
sublimate  of  S.  When  heated  to  fusion  it  yields  a  sublimate  of  arsenic 
sulphide  The  mineral  is  soluble  in  aqua  regia 

Enargite  is  easily  recognized  by  its  crystallization  and  blowpipe 

Occuiience. — Enargite  is  associated  with  other  copper  ores  in  veins 
filled  by  magmatiC  water  at  intermediate  depths  and  in  a  few  replace- 
ment deposits 

Localities  — Although  not  widely  distributed,  enargite  occurs  in  large 
quantities  in  the  copper  mines  near  Morococha,  Peru;  Copiap6,  Chile; 
in  the  province  of  La  Rioja,  Argentine;  on  Luzon,  Philippine  Islands, 


and  in  the  United  States,  at  Butte,  Montana    in  the  San  Juan  Moun- 
tains, Colorado   and  m  the  Tmtic  District,  Utah 

Uses  —It  is  smelted  as  an  ore  of  copper  At  the  Butte  smelter  it 
furnishes  the  arsenic  that  is  separated  from  the  smelter  fumes  and  placed 
upon  the  market  as  arsenic  oxide  (see  p  113) 


The  basic  sulpho-salts  are  compounds  in  \\hich  there  is  a  greater 
percentage  of  the  basic  elements  (metals,  etc),  present  than  is 
necessary  to  replace  all  the  hydrogen  of  the  ortho  acids  Thus,  the 
copper  orthosulpharsenate,  enargite,  is  CusAsSU  The  mineral  steph- 
anite  is  AgsSbS*  and  the  pure  silver  polybasite  AggSbSe 

Since  three  atoms  of  Ag  are  sufficient  to  replace  all  the  hydrogen 
atoms  m  the  normal  acid  containing  one  atom  of  antimony  and  the 
quantities  of  silver  present  in  stephamte  and  polybasite  are  in  excess 
of  this  requirement,  the  two  minerals  are  described  as  basic  The 
exact  relations  of  the  atoms  to  one  another  in  the  molecules  are 
not  known 

Although  the  number  of  basic  sulpho-salts  occurring  as  minerals  is 
large  only  four  are  common  These  are: 

Stephamte  AgoSbS*  Orthorhombic 

Polybasite  (Ag  -  Cu^SbSc  Monoclimc 

Tetrahednte  (R")4Sb2S7  Isometric 

T&nnantite  (R'^AsoS?  Isometric 

Stephanite  (Ag5SbS4) 

Stephanite,  though  a  comparatively  rare  mineral,  is  an  important  ore 
of  silver  in  some  camps  It  occurs  massive,  in  disseminated  grains  and 
as  aggregates  of  small  crystals  Analyses  indicate  a  composition  very 
dose  to  the  requirements  of  the  formula  AgsSbS4 

S         Sb        Ag      AsandCu     Total 

Theoretical  .  . .   16  28    15  22    68  50  100  oo 

Crystals,  Chanarollo,  Chile  16  02    15  22    68  65          tr  99  89 

Stephanite  crystallizes  in  hemimorphic  orthorhombic  crystals  (rhom- 
bic pyramidal  class),  with  an  axial  ratio  .6291  :  i :  .6851.  The  crystals 
are  highly  modified,  125  forms  having  been  identified  upon  them.  They 
have  usually  the  habit  of  hexagonal  prisms,  their  predominant  planes 


being  ooP(no)  and  oop  06(010),  terminated  by  oP(ooi),  P(in)  and 
2Poc  (021)  at  one  or  the  other  end  of  the  c  aus  (Fig  54)  Twins  are 
common,  with  oo  P(no)  and  oP(ooi)  the  t\\ inning  planes 

The  mineral  is  black  and  opaque  and  its  streak  is  black     Its  hard- 
ness is  2  and  density =6  2  —  63      It  cleaves 
parallel  to  oo  P  06  (oio)  has  an  uneven  frac- 
ture, and  is  a  poor  conductor  of  electricity 

On  charcoal  stephamte  fuses  \ery  easily 
to  a  dark  gray  globule,  at  the  same  time 
yielding  the  \vhite  fumes  of  antimony  oxide  FIG.  54 —Stephanite  Crystal 
and  the  pungent  odor  of  S02  Under  the  *»th  oP,  oox  («),  <*?£, 
reducing  flame  the  globule  is  reduced  to  oio(ft)  ooP,  !io  W,  |P, 

,,          ,  m-,  i      T      t          -         S32  (P)> "°° » °21  W- 

metallic   silver.     The   mineral    dissolves  in 

dilute  nitric  acid  and  this  solution  gives  a  white  precipitate  with  HC1. 

Stephamte  is  easily  distinguished  from  other  black  minerals  by  its 
easy  fusibility,  its  crystallization,  and  its  reactions  for  Ag,  Sb  and  S 

Localities — The  mineral  is  associated  Tvith  other  silver  ores  in  the 
zone  of  secondary  enrichment  of  veins  at  Freiberg,  Saxony,  Joachimsthal 
and  Pribram,  Bohemia,  the  Comstock  Lode  and  other  mines  in  the 
Rocky  Mountain  region  and  at  many  points  in  Mexico  and  Peru. 

Uses  — It  is  mined  together  with  other  compounds  as  an  ore  of  silver 
It  is  particularly  abundant  in  the  ores  of  the  Comstock  Lode,  Nev.,  and 
of  the  Las  Chispas  Mine,  Sonora,  Mex. 

Polybasite  ((Ag-Cu)9SbS6) 

Polybasite  is  the  name  usually  applied  to  the  mixture  of  basic  sulph- 
ai^fomtes  and  sulpharsemtes  of  the  general  formula  R^Sb-AsJSe,  in 
which  R'= Ag  and  Cu.  More  properly  the  name  is  applied  to  the  anti- 
monite,  and  the  corresponding  arsenite  is  designated  as  pearceite.  Sev- 
eral typical  analyses  follow 

S  As         Sb  Ag  Cu  Fe       Pb       Ins  Total 

I    17  46  7  56      .     .  59  22  15  65                            -  99  89 

H-   17  7i  7  39        •  SS-I7  *S  ii  i  05                 42  99  85 

HI.    15  43  5°  10.64  68  39  $  13  .            .  100  09 

IV.    16  37  3  88  5  is  6793  607          .      .76      ...  100.18 

I  Pearceite  Veta  Rica  Mine,  Sierra  Mojada,  Mexico 
II.  Crystals  of  pearceite,  Drumlummon  Mine,  Marysville,  Montana. 

III.  Polybasite,  Santa  Lucia  Mine,  Guanajuato,  Mexico 

IV.  Polybasite,  Quespisiza,  Clule 


The  crystallization  of  the  two  minerals,  which  are  completely  isomor- 
phous,  is  monoclinic  (prismatic  class)     Their  axial  ratios  are 

Pearceite,       a  :  b  :  c=  1.7309  :  i :  i  6199       £=9°°  9' 
Polybasite,  =i  7309  :  i  :  i  5796       £=90' 



The  crystals  are  commonly  tabular  or  prismatic,  with  a  distinct 
hexagonal  habit.  The  prominent  forms  are  oP(ooi),  P(ni)  and 
2P  55  (20!).  Contact  twinning  is  common,  with  oo  P(no)  the  twinning 
plane,  and  oP(ooT)  the  composition  plane 

Both  minerals  are  nearly  opaque  Except  in  very  thin  splinters 
they  are  steel-gray  to  iron-black  in  color  Very  thin  plates  are  trans- 
lucsnt  and  cherry-red  Their  streaks  are  black  Their  cleavage  is 
perfect  parallel  to  oP(ooi)  and  their  fracture  uneven  Their  hardness 
is  2-3,  and  density  6-6  2 

Both  minerals  are  easily  fusible  They  usually  exhibit  the  reactions 
for  Ag,  Sb,  As  and  S 

They  are  readily  distinguished  from  all  other  minerals  but  silver 
sulpho-salts  by  their  blowpipe  reactions  From  these  they  are  distin- 
guished by  their  crystallization  Pearceite  and  polybasite  are  distin- 
guished from  one  another  by  the  relative  quantities  of  As  and  Sb  they 

Occurrence  — Both  minerals  occur  in  the  zone  of  secondary  enrich- 
ment in  veins  of  silver  sulphides. 

Localities  — Polybasite  was  an  important  ore  of  silver  in  the  Comstock 
Lode,  Nevada  It  is  at  present  mined  with  other  silver  ores  at  Ouray, 
Colorado,  at  Marysville,  Montana,  at  Guanajuato,  Mexico,  and  at 
various  points  in  Chile  Good  crystals  occur  at  Freiberg,  Saxony,  at 
Joachimsthal,  Bohemia,  and  in  the  mines  in  Colorado,  Mexico  and  Chile. 


The  name  tetrahedrite  is  given  to  a  mixture  of  basic  sulphanti- 
monites  and  sulpharsenites  crystallizing  together  in  isometric  forms  with 
a  distinct  tetrahedral  habit  (hextetrahedral  dass)  The  isomorphism 
is  so  complete  that  all  gradations  between  the  various  members  of  the 
group  are  frequently  met  with  The  arsenic-bearing  member  of  the 
series  is  known  as  tennantite  and  the  corresponding  antimony  member  as 
letrakednte  The  latter  is  the  more  common 

The  following  six  analyses  of  tetrahedrite  will  give  some  idea  of  the 
great  range  in  composition  observed  in  the  species. 


S        Sb      As      Cu  Fe  Zn      Ag  Hg     Pb      Total 

I   27  60  25  87    tr  35  85  2  66  5  15     2  30  99  43 

II   23  51  17  21  7  67  42  oo  8  28  49        55  99  71 

III.  24  44  27  60  27  41  4  27  2  31  14  54  .         100  57 

IV    24  89  30  18    tr  32  80  5  85  07  5  57                99  36 

V    21  67  24  72  33  53  56  i  So  16  23      98  51 

I  Xewbur>port,  Mass 

II  Cajabamba,  Peru 

HI  Star  City,  Xev 

IV  Poracs,  Hungary. 

V  Arizona. 

Upon  examination  these  are  found  to  correspond  approximately  to 
the  formula  R' ^SbaS:,  in  which  the  R"  is  Cu2,  Pb,  Fe,  Zn,  Hg,  Ag2  and 
sometimes  Co  and  Ni  When  R  is  replaced  entirely  by  copper,  the 
formula  (CusSb2S-)  demands  23  i  per  cent  S,  24  8  per  cent  Sb  and  52  i 
per  cent  Cu 

Analyses  of  tennantite  yield  analogous  results  that  may  be  repre- 
sented by  the  formula  CusAs2Sr  which  demands  26  6  per  cent  S,  20  76 
per  cent  As  and  52  64  per  cent  Cu 

Analyses  of  even  the  best  crystallized  specimens  rarely  yield  As  or 
Sb  alone.  Moreover,  nearly  all  show  the  presence  of  Zn  in  notable 
quantity  The  great  variation  noted  in  the  composition  of  different 
specimens  which  appear  to  be  pure  crystals  has  led  to  the  proposal  of 
other  formulas  than  those  given  abo\e — some  being  simpler  and  others 
more  complex  It  is  possible  that  the  variation  may  be  explained  as 
due,  in  part,  to  some  kind  of  solid  solution,  rather  than  as  the  result 
solely  of  isomorph'jus  replacement  It  is  more  probable,  however,  that 
it  is  due  to  the  intergrowth  of  notable  quantities  of  various  sulphides 
with  the  sulpho-salts 

There  is  still  considerable  confusion  in  the  proper  naming  of  the  mem- 
bers of  the  series,  but  generally  the  forms  composed  predominantly  of 
Cu,  Sb  and  S  with  or  without  Zn  are  known  as  tetrahednte  and  those 
containing  As  m  place  of  Sb  as  tennantite,  although  several  authors 
confine  the  use  of  the  latter  term  to  arsenical  tetrahedrites  containing  a 
notable  quantity  of  iron 

Since  the  members  of  the  tetrahedrite  series  often  contain  a  large 
quantity  of  metals  other  than  Cu  and  Zn  the  group  has  been  so  sub- 
divided as  to  indicate  this  fact  Thus,  there  are  argentiferous,  mercurial 
and  plumbiferous  varieties  of  tetrahedrite  Some  of  these  varieties  are 
utilized  as  ores  of  the  metals  that  replace  the  copper  and  zinc  in  the  more 


common  varieties  The  relations  of  the  ordinary  (II)  and  the  bis- 
muthiferous  tennantites  (III)  to  tetrahednte  (I)  are  shown  by  the  fol- 
lowing three  analyses. 

S         As        Sb  Bi        Cu  Fe  Ag        Pb        Co  Total 

I     24  48       tr  28  85  45  39  i  3*  "  IQo  15 

II     26  61  19  03  51  62  i  95  99  21 

III      29  10  ii  44      2  19  13  07    37  52  6  51  04  i  20        101  07 

I   Fresney  d'Oisans,  France. 
II   Cornwall,  England. 
Ill  Cremenz,  Switzerland 

The  crystals  of  both  tetrahedrite  and  tennantite  are  tetrahedral  in 
habit,  the  principal  forms  on  them  consisting  of  the  simple  tetrahedron 

and  complex  tetrahedrons  such  as  —(211),  — —  (332)  together  with 

the  dodecahedron,  ooQ(iio)  and  the  cube,  ooOoo(ioo)  (Fig.  55) 
Twins  are  common  with  0(in)  the  twinning 
plane.  These  are  sometimes  contact  twins 
and  sometimes  interpenetration  twins.  Some 
crystals  are  very  complicated,  because  of  the 
presence  on  them  of  a  great  number  of  forms 
The  total  number  of  distinct  forms  that  have 
been  identified  is  about  90.  The  mineral 

m      L  j      ^       occurs  also  in  granular,  dense  and   earthy 
FIG  55  —Tetrahednte  Crys-  6  '  J 

o  masses. 

tal  with  -,  1 1 1  W ,  "»  o,        The  fracture  of  the  tetrahedrites  is  uneven 

no  (d)  and  fO,  332  (»).     Their  hardness  varies  between  3  and  4  5  and 

their  density  between  4  4  and  5  i     Their  color 

is  between  dark  gray  and  iron-black,  except  in  thin  splinters,  which 
sometimes  exhibit  a  cherry-red  translucency.  Their  streak  is  like  their 
color.  All  tetrahedrites  are  thermo-electric. 

The  chemical  properties  of  the  different  varieties  of  tetrahedntes 
vary  with  the  constituents  present.  All  give  tests  for  sulphur  and  for 
either  antimony  or  arsenic,  and  all  show  the  presence  of  copper  in  a 
borax  bead.  The  reactions  of  other  metals  that  may  be  present  may 
be  learned  by  consulting  pages  483-494. 

The  crystals  of  tetrahedrite  are  so  characteristic  that  there  is  little 
danger  of  confusing  the  crystallized  mineral  with  other  minerals  of  the 
same  color.  The  massive  forms  resemble  most  dearly  arseno$yritey 
lownmtie  and  chalcocite  From  these  the  tetrahedrites  are 


best  distinguished  by  their  hardness,  together  with  their  blowpipe  reac- 

Tetrahednte  appears  to  suffer  alteration  quite  readily,  since  pseudo- 
morphs  of  several  carbonates  and  sulphides  after  tetrahednte  crystals 
are  well  known 

Syntheszs  — Crystals  of  the  tetrahedrites  have  been  made  by  passing 
the  vapors  of  the  chlorides  of  the  metals  and  the  chlorides  of  arsenic  or 
antimony  and  EfeS  through  red-hot  porcelain  tubes  They  have  also 
been  observed  in  Roman  coins  that  had  Iain  for  a  long  time  in  the  hot 
springs  of  Bourbonne-les-Bains,  Haute-Marne,  France. 

Occurrence — The  tetrahedrites  are  very  common  in  the  zone  of 
secondary  enrichment  of  sulphide  veins  and  in  impregnations  They 
occur  associated  with  chalcopyrite,  pynte,  sphalerite,  galena  and  other 
silver,  lead  and  copper  ores  in  nearly  all  regions  where  the  sulphide  ores 
of  these  metals  are  found  They  occur  also  as  primary  constituents  of 
veins  of  silver  ores,  where  they  were  deposited  by  magmatic  waters. 

Localities  — In  the  United  States  tetrahedrite  occurs  at  the  Kellogg 
Mines,  ten  miles  north  of  Little  Rock,  Arkansas,  near  Central  City  and 
at  Georgetown,  Colorado;  in  the  Ruby  and  other  mining  districts  in 
the  same  State;  at  the  De  Soto  Mine  in  Humboldt  Co ,  Nevada,  and 
at  several  places  in  Montana,  Utah  and  Arizona  It  is  found  also  in 
British  Columbia  and  in  Mexico,  and  at  Broken  Hill,  New  South  Wales 

The  arsenical  tetrahedrites  are  not  quite  as  common  as  is  the  anti- 
monial  variety  Excellent  crystals  occur  in  the  Cornish  Mines,  at 
Freiberg  in  Saxony,  at  Skutterud  in  Norway,  and  at  Capelton, 

Uses. — The  mineral  is  used  to  some  extent  as  an  ore  of  silver  or  of 
copper,  the  separation  of  the  metals  being  effected  in  the  same  way  as 
in  the  case  of  the  sulphides  of  these  substances. 


Only  two  sulpho-f  emtes  are  sufficiently  important  to  merit  descrip- 
tion here  Both  of  these  are  copper  compounds  and  both  are  used  as 
ores  of  this  metal,  one — chalcopyrite — being  one  of  the  most  important 
ores  of  the  metal  at  present  worked 

The  first  of  these  minerals  discussed,  bornite,  is  a  basic  salt  of 
the  acid  EfeFeSa,  the  second  is  the  salt  of  the  derived  acid  HFeS2, 
which  may  be  regarded  as  the  normal  acid  from  which  one  molecule  of 
H2S  has  been  abstracted  (see  p.  n6], 


Bornite  (Cu5FeS4) 

Bormte,  known  also  as  horseflesh  ore  because  of  its  peculiar  purplish- 
red  color,  is  found  usually  massive  In  Montana  and  in  Chile  it  con- 
stitutes an  important  ore  of  copper 

Bornite  is  probably  a  basic  sulpho-femte,  though  analyses  yield 
lesults  that  vary  quite  widely,  especially  in  the  case  of  massive  varieties 
This  variation  is  due  to  the  greater  or  less  admixture  of  copper  sulphides, 
mainly  chalcocite,  with  the  bormte  The  theoretical  composition  of  the 
mineral  is  25  55  S,  63  27  Cu,  and  11.18  Fe  The  analyses  of  a  crystallized 
variety  from  Bristol,  Conn  ,  and  of  a  massive  variety  from  the  Bruce 
Mines,  Ontano,  follow. 

S          Cu        Fe      Ins     Total 

Bristol,  Conn  .  25  54    63  24    n  20  99  98 

Bruce  Mines,  Ont  25  39    62  78    n  28      30    99  75 

The  crystallization  of  bormte  is  isometric  (hexoctahedral  class),  in 
combinations  of  oo  O  oo  (ico),  oo  0(iio),0(rn),  and  sometimes  202(211) 
Crystals  often  form  mterpenetration  twins,  with  0  the  twinning  plane 

The  fracture  of  the  mineral  is  conchoidal,  its  hardness  3  and  density 
about  5  On  fresh  fracture  the  color  varies  from  a  copper-red  to  a  pur- 
plish brown  Upon  exposure  alteration  rapidly  takes  place  covering 
the  mineral  with  an  iridescent  purple  tarnish.  Its  streak  is  grayish 
black  It  is  a  good  conductor  of  electricity 

Chemically,  the  mineral  possesses  no  characteristics  other  than  those 
to  be  expected  from  a  compound  of  iron,  copper  and  sulphur  It  dis- 
solves in  nitric  acid  with  the  separation  of  sulphur 

It  is  easily  recognized  by  its  purplish  brown  color  on  fresh  fractures 
and  its  purple  tarnish. 

Bornite  alters  to  chalcopyrite,  chalcocite.  covellite,  cuprite  (CuaO), 
chrysocolla  (CuSiQs  2H20)  and  the  carbonates,  malachite  and  azurite. 
On  the  other  hand,  bornite  pseudomorphs  after  chalcopyrite  and  chal- 
cocite are  not  uncommon 

Syntheses — Roman  copper  coins  found  immersed  in  the  water  of 
warm  springs  in  France  have  been  partly  changed  to  bornite.  Crystals 
have  been  formed  by  the  action  of  EkS  at  a  comparatively  low  tempera- 
ture (ioo°-2oo°  C  ),  upon  a  mixture  of  CuaO,  CuO  and  Fe20s 

Occurrence  and  Origin — Bornite  is  usually  associated  with  other 
copper  ores  in  veins  and  lodes,  where  it  is  in  some  cases  a  primary  min- 
eral deposited  by  magmatic  waters  and  in  others  a  secondary  mineral 
produced  in  the  zone  of  enrichment  of  sulphide  veins.  It  also  sometimes 


impregnates  sedimentary  rocks,  where  its  origin  is  part  due  to  contact 

Localities  — The  crystallized  mineral  occurs  near  Redruth,  Cornwall 
Eng ,  and  at  Bristol,  Conn  The  massive  mineral  is  found  at  many 
places  in  Norway  and  Sweden  It  is  the  principal  ore  of  some  of  the 
Bolivian,  Chilian,  Peruvian  and  Mexican  mines  and  of  the  Canadian 
mines  near  Quebec  In  the  United  States  it  has  been  mined  at 
Bristol,  Conn  ,  and  at  Butte,  Montana 

Uses — Bornite  is  mined  with  chalcopyrite  and  other  copper  com- 
pounds as  an  ore  of  this  metal 

Chalcopynte  (CuFeS2) 

From  an  economic  point  of  \ie\\  this  mineral  is  the  most  important 
of  the  sulpho-salts,  as  it  is  one  of  the  most  important  ores  of  copper 

FIG  56  FIG  57  FIG  58 

FIG.  56  —Chalcopynte  Crystal  with  P,  in  (p),  -P,  ill  (p)  and  2?  x> ,  201  (3). 

IP  Pz 

FEG  57 — Chalcopynte  Crystal  with  — ,  772  (&J  and  — ,  212  (x)       The  form  ^ 

2  2 

sometimes  approaches  «  P(zio)  and  x  approaches  P  *s  (xoi1) 
FIG  58  — Chalcopynte  Twinned  about  P(iu) 

known.  It  occurs  both  massive  and  crystallized.  From  its  similarity 
to  pyrite  in  appearance  it  is  often  known  as  copper  pyrites. 

Crystallized  specimens  of  chalcopyrite  contain  35  per  cent  S,  34  5 
per  cent  Cu  and  30.5  per  cent  Fe,  corresponding  to  the  formula  CuFeSk, 
i  e ,  a  copper  salt  of  the  acid  HFeS2  The  mineral  often  contains  small 
quantities  of  intermixed  pyrite.  It  also  contains  in  some  instances 
selenium,  thallium,  gold  and  silver 

The  crystallization  of  chalcopynte  is  in  the  sphenoidal,  hemihedral 
division  of  the  tetragonal  system  (tetragonal  scalenohedron  class). 


The  crystals  are  usually  sphenoidal  in  habit  with  the  sphenoids  -(in), 


and  —(332)  the  predominant  forms  (Figs  56  and  57)     In  addition  to 


these  there  are  often  present  also  oo  P  oo  (100),  oo  P(no),  2?  oo  (201), 

and  a  very  acute  sphenoid  that  is  approximately  — (772),  supposed  to  be 


due  to  the  oscillation  of  oo  P(no)  and  -(in)  (Fig  57)     Twins  are  quite 

common,  with  the  twinning  plane  parallel  to  P  (Fig  58).  The  plus 
faces  of  the  sphenoid  are  often  rough  and  striated,  while  the  minus  faces 
are  smooth  and  even. 

The  fracture  of  the  mineral  is  uneven.  Its  hardness  is  3  5-4  and 
density  about  4.2.  Its  luster  is  metallic  and  color  brass-yellow  Old 
fracture  surfaces  are  often  tarnished  with  an  iridescent  coating  Its 
streak  is  greenish  black.  It  is  an  excellent  conductor  of  electricity 

On  charcoal  the  mineral  melts  to  a  magnetic  globule.  When  mixed 
with  Na2COs  and  fused  on  charcoal,  a  copper  globule  containing  iron 
results.  When  treated  with  nitric  aad  it  dissolves,  forming  a  green 
solution  in  which  float  spongy  masses  of  sulphur  The  addition  of 
ammonia  to  the  solution  changes  it  to  a  deep  blue  color  and  at  the  same 
time  causes  a  precipitate  of  red  feme  hydroxide. 

From  the  few  brassy  colored  minerals  that  resemble  it,  chalcopyrite 
is  distinguished  by  its  hardness  and  streak. 

When  subjected  to  the  action  of  the  atmosphere  or  to  percolating 
atmospheric  water  chalcopyrite  loses  its  iron  component  and  changes 
to  covelhte  and  chalcocite  The  iron  passes  into  limomte.  Bornite, 
copper  and  pyrite  are  also  frequent  products  of  its  alteration.  In  the 
oxidation  zone  of  veins  it  yields  limonite,  the  carbonates,  malachite  and 
azurite,  and  cuprite  (Cu20).  When  exposed  to  the  leaching  action  of 
water,  limonite  alone  may  remain  to  mark  the  outcrop  of  veins,  the 
copper  being  carried  downward  in  solution  to  enrich  the  lower  portions 
of  the  vein.  The  deposit  of  limonite  on  the  surface  is  known  as 

Syntheses — Crystals  of  chalcopyrite  have  been  produced  by  the 
action  of  HaS  upon  a  moderately  heated  mixture  of  CuO  and  F^Os 
cndosed  in  a  glass  tube.  The  mineral  has  also  been  made  by  the  action 
of  warm  spring  waters  upon  ancient  copper  coins.  It  is  also  a  fairly 
common  product  of  roasting-oven  operations 

Occurrence  and  Origin.— Chalcopyrite  is  widely  disseminated  as  a 
primary  vein  mineral,  and  is  often  found  in  nests  in  crystalline  rocks. 


It  also  impregnates  slates  and  other  sedimentary  rocks,  schists  and 
altered  igneous  rocks  where,  in  some  cases,  it  is  a  contact  deposit 
and  in  others  is  original  It  is  also  formed  by  secondary  processes  caus- 
ing enrichment  of  copper  sulphide  veins  Its  most  common  associ- 
ates are  galena,  sphalerite  and  pyrite.  It  is  the  principal  copper  ore 
m  the  Cornwall  mines,  where  it  is  associated  with  cassitente  (Sn02), 
galena  and  other  sulphides.  It  is  also  the  important  copper  ore  of 
the  deposits  of  Falun,  Sweden,  of  Namaqualand  in  South  Africa, 
those  near  Copiapo  in  Chile,  those  of  Mansfeld,  Germany,  of  the  Rio 
Tinto  district  in  Spain,  of  Butte  and  other  places  in  Montana,  and  of 
the  great  copper-producing  districts  in  Arizona,  Utah  and  Nevada. 

Crystals  occur  near  Rossie,  Wurtzboro  and  Edenville,  N.  Y.,  at  the 
French  Creek  Mines,  Chester  Co.,  Penn.,  near  Finksburg,  Md.,  and  at 
many  other  places 

Extraction — The  mineral  is  concentrated  by  mechanical  methods. 
The  concentrates  are  roasted  at  a  moderately  high  temperature,  the  iron 
being  transformed  into  oxides  and  the  copper  partly  into  oxide  and 
partly  into  sulphide.  Upon  further  heating  with  a  flux  the  iron  oxide 
unites  with  this  to  form  a  slag  and  the  copper  sulphide  melts,  and  collects 
at  the  bottom  of  the  furnace  as  "  matte/'  which  consists  of  mixed  copper 
and  copper  sulphide.  This  is  roasted  in  a  current  of  air  to  free  it  from 
sulphur.  By  this  process  all  of  the  copper  is  transformed  into  the  oxide, 
which  may  be  converted  into  the  metal  by  reduction.  The  metal  is 
finally  refined  by  electrical  processes.  Much  of  the  copper  obtained 
from  chalcopyrite  contains  silver  or  gold,  or  both,  which  may  be  recov- 
ered by  any  one  of  several  processes. 

Uses.— A  large  portion  of  the  copper  produced  in  the  world  is  obtained 
by  the  smelting  of  chalcopyrite  and  the  ores  associated  with  it. 

Production.— The  world's  total  product  of  copper  has  been  referred 
to  in  another  place  (p.  55).  Of  this  total  (2,251,300,000  Ib.)  the  United 
States  supplied,  in  1912, 1,243,300,000  Ib.,  of  which  about  1,000,000,000 
Ib.  were  obtained  from  sulphide  ores.  Arizona  and  Montana  produced 
the  greater  portion  of  this  large  quantity,  the  former  contributing  about 
359,000,000  Ib.  to  the  aggregate,  and  the  latter  308,800,000  Ib  Out- 
side of  the  United  States  the  most  important  copper-producing  countries 
are  Mexico,  Japan,  Spain  and  Portugal,  Australia,  Chile,  Canada, 
Russia,  Peru  and  Germany,  in  the  order  named.  Practically  all  of  this 
copper,  except  that  from  Japan  and  Mexico,  is  extracted  from  sulphide 



THE  salts  belonging  to  this  group  are  'compounds  of  metals  with 
hydrochloric  (HC1),  h>drobromic  (HBr),  hydnodic  (HI)  and  hydro- 
fluoric (HF)  acids  Only  a  few  are  of  importance  Of  these  some  are 
simple  chlorides,  others  are  simple  fluorides,  others  are  double  chlorides 
or  fluorides  (i  e  cryolite,  AlFa^NaF),  and  others  are  double  hydrox- 
ides and  chlorides  (atacamite) 


The  simple  chlorides  crystallize  in  the  isometric  system,  but  in  differ- 
ent classes  in  this  system.  They  comprise  salts  of  the  alkalies,  K,  Na 
and  NKi,  and  of  silver  Of  these  only  three  mmerals  are  of  importance, 
viz.:  sylmte,  hahte  and  cerargynte 

Halite  (Had) 

Halite,  or  common  salt,  is  the  best  known  and  most  abundant  of  the 
native  chlorides  It  is  a  colorless,  transparent  mineral  occurring  in 
crystals,  and  in  granular  and  compact  masses 

Pure  halite  consists  of  39  4  per  cent  Cl  and  60  6  per  cent  Na  The 
mineral  usually  contains  as  impurities  clay,  sulphates  and  organic 
substances  The  several  analyses  quoted  below  indicate  the  nature  of 
the  commonest  impurities  and  their  abundance  in  typical  specimens 

NaCl      CaCl     MgCl     CaS04      Na2S04     Mg2S04  Clay     H20 

I   97  35  ...        i  01  43  23  30 

II.  90  3          „  .  5  oo          2  oo  2  oo        70 

III,  98  88         tr          tr          .79          33 

I   Stassfurt,  Germany. 
II   Vic,  France 
III.  Petit  Anse,  La. 

The  crystallization  of  halite  is  isometric  (hexoctahedral  class),  the 
principal  forms  being  ooOoo(ioo),  0(iu)  and  ooO(no)  Often  the 



faces  of  the  forms  are  hollowed  or  depressed  giving  nse  to  what  are  called 
"  hopper  crystals  "  (Fig  59).  The  mineral  occurs  also  in  coarse,  gran- 
ular aggregates,  in  lamellar  and  fibrous  masses  and  in  stalactites 

Its  cleavage  is  perfect  parallel  to  oo  0  oo  (100)     Its  fracture  is  con- 
choidal     Its  hardness  is  2-2  5  and  density  about  217     Halite,  when 
pure,  is  colorless,  but  the  impurities  present  often  color  it  red,  gray, 
yellow  or  blue     The  bright  blue  motthngs  obsened  in 
many  specimens  are  thought  to  be  due  to  the  presence 
of  colloidal  sodium.    The  mineral  is  transparent  or 
translucent  and  its  luster  is  \itreous.    Its  streak  is 
colorless      Its  saline  taste    is  well   known.     It   is 
diathermous  and   is  a  nonconductor  of   electricity.  prG  59— Hcpper- 
The  mineral  is  plastic  under  pressure  and  its  plasticity     Shaped  Cube  of 
increases  with  the  temperature    Its  index  of  refraction      Halite 
for  sodium  light,  «=  i  5442 

In  the  closed  tube  halite  fuses  and  often  it  decrepitates.  When 
heated  before  the  blowpipe  it  fuses  (at  776°)  and  colors  the  flame  yellow. 
The  chlorine  reaction  is  easily  obtained  by  adding  a  small  particle  cf  the 
mineral  to  a  microcosmic  salt  bead  that  has  been  saturated  with  copper 
oxide.  This,  when  heated  before  the  blowpipe,  colors  the  flame  a  bnl- 
hant  blue.  The  mineral  easily  dissolves  in  water,  and  its  solution  yields 
an  abundant  white  precipitate  with  silver  nitrate. 

The  solubility  of  halite  is  accountable  for  a  large  number  of 
pseudomorphs.  The  crystals  embedded  in  clays  are  gradually  dissolved, 
leaving  a  mold  that  may  be  filled  by  other  substances,  which  thus 
become  pseudomorphs. 

Syntheses.— Crystals  of  halite  have  been  produced  by  sublimation 
from  the  gases  of  furnaces,  and  by  crystallization  from  solution  contain- 
ing sodium  chloride. 

Occurrence  and  Origin  —Salt/occurs  most  abundantly  in  the  water  of 
the  ocean,  of  certain  salt  lakes,  of  brines  buned  deep  within  the  rocks  in 
some  places,  and  as  beds  interstratified  with  sedimentary  rocks.  In  the 
latter  case  it  is  associated  with  sylvite  (KC1),  anhydrite  (CaSO*),  gypsum 
(CaSO4  2H2O),  etc.,  which,  lite  the  halite,  are  believed  to  have  been 
formed  by  the  drying  up  of  salt  lakes  or  of  portions  of  the  ocean  that 
were  cut  off  from  the  main  IxxLy  of  water,  since  the  order  of  occurrence 
of  the  various  beds  is  the  sa  me  as  the  order  of  deposition  ot  the  corre- 
sponding salts  when  precipitated  by  the  evaporation  of  sea  water  at 
varying  temperatures  (Ojanp  pp.  22,  23.) 

Below  are  given  figures*  showing  the  composition  of  the  salts  in  the 
water  of  the  ocean,  of  GF -at  Salt  Lake,  and  of  the  Syracuse,  N.  Y.»  and 


Michigan  artificial  brines  (produced  by  forcing  water  to  the  buned  rock 

NaCl  CaCk  MgCl2  NaBr  KC1  Na2S04  K2S04  CaS04  MgS04 
I   77  07  7  86    i  30    3  89  4  63      5  29 

II.  79  57  10  oo  6  25      3  60          58 

III  95  97        90        69  .  2  54 

IV.  91  95    3  19    2  48  2  39 

I  Atlantic  Ocean 

II   Great  Salt  Lake 

HI  New  York  bnnes 

IV  Michigan  bnnes 

Localities  —The  principal  mines  of  halite,  or  rock  salt,  are  at  Wie- 
liczka,  Poland,  Hall,  Tyrol,  Stassfuit,  Germany,  where  fine  crystals 
are  found,  the  Valley  of  Cardova,  Spain,  in  Cheshire,  England  and  in 
the  Punjab  region  of  India  At  Petit  Anse  in  Louisiana,  in  the  vicinity 
of  Syracuse,  N  Y ,  and  in  the  lower  peninsula  of  Michigan  thick  beds 
of  the  salt  are  buried  in  the  rocks  far  beneath  the  surface  Much  of  the 
salt  is  comparatively  pure  and  needs  only  to  be  crushed  to  become  usable 
In  most  cases,  however,  it  is  contaminated  with  clay  and  other  sub- 
stances In  these  cases  it  must  be  dissolved  in  water  and  recrystallized 
before  it  is  sufficiently  pure  for  commercial  uses 

The  best  known  deposits  are  at  Stassfurt  where  there  is  a  great  thick- 
ness of  alternating  layers  of  halite,  sylvite  (KC1),  anhydrite,  gypsum, 
kieseiite  (MgSQa-IfeO)  and  various  double  chlorides  and  sulphates  of 
potassium  and  magnesium.  Although  the  halite  is  in  far  greater  quan- 
tity than  the  other  salts,  nevertheless,  the  deposit  owes  most  of  its  value 
to  the  latter,  especially  the  potassium  salts  (comp.  pp.  137,  142) 

Uses. — Besides  its  use  in  curing  meat  and  fish,  salt  is  employed  in 
glazing  pottery,  in  enameling,  in  metallurgical  processes,  for  clearing 
oleomargarine,  making  butter  and  in  the  more  familiar  household  oper- 
ations. It  is  also  the  chief  source  of  sodium  compounds. 

Production  —Most  of  the  salt  produced  in  the  United  States  is  ob- 
tained directly  from  rock  salt  layers  by  mining  or  by  a  process  of  solu- 
tion, in  which  water  is  forced  down  into  the  buned  deposit  and  then  to 
the  surface  as  bnne,  which  is  later  evaporated  by  solar  or  by  artificial 
heat  In  the  district  of  Syracuse,  N.  Y ,  salt  occurs  in  thick  lenses 
interbedded  with  soft  shales  In  eastern  Michigan  and  in  Kansas  salt 
is  obtained  from  buried  beds  of  rock  salt,  and  in  Louisiana  from  great 
dome-like  plugs  covered  by  sand,  day  and  gravel.  Some  of  the  masses 
in  this  State  are  1,756  ft.  thick. 


The  salt  production  of  the  United  States  for  1912  amounted  to  33,- 
324,000  barrels  of  280  Ib  each,  valued  at  $9,402,772  Of  this  quantity 
7,091,000  barrels  were  rock  salt 

The  imports  of  all  grades  of  salt  during  the  same  time  were  about 
1,000,000  barrels  and  the  exports  about  440,000  barrels. 

Sylvite  (KC1) 

Sylvite  is  isometric,  like  halite,  but  the  etched  figures  that  may  be 
produced  on  the  faces  of  its  crystals  indicate  a  gyroidal  symmetry  (pen- 
tagonal icositetrahedral  class)  The  habit  of  the  crystals  is  cubic  with 
O(ni)  and  oo  O  oo  (100)  predominating. 

Pure  sylvite  contains  47  6  per  cent  Cl  and  52  4  per  cent  K,  but  the 
mineral  usually  contains  some  NaCl  and  often  some  of  the  alkaline  sul- 

The  physical  properties  of  sylvite  are  like  those  of  halite,  except  that 
its  hardness  is  2  and  the  density  i  99  Its  melting  temperatuie  is  738° 
and  n  for  sodium  light  =  i  4903 

When  heated  before  the  blowpipe  the  mineral  imparts  a  violet  tinge 
to  the  flame,  which  can  be  detected  when  masked  by  the  yellow  flame  of 
sodium  by  viewing  it  through  blue  glass  Otherwise  sylvite  and  halite 
react  similarly. 

Halite  and  sylvite  are  distinguished  from  other  soluble  minerals  by 
the  reaction  with  the  bead  saturated  with  copper  oxide,  and  from  one 
another  by  the  color  imparted  to  the  blowpipe  flame. 

Synthesis  — Sylvite  crystals  have  been  made  by  methods  analogous 
to  those  employed  in  syntheses  of  halite  crystals 

Occurrence — Sylvite  occurs  associated  with  halite,  but  in  distinct 
beds,  at  Stassfurt,  Germany,  and  at  Kalusz,  Galicia.  It  has  also  been 
found,  together  with  the  sodium  compound,  incrusting  the  lavas  of 

Uses. — Sylvite  Is  an  important  source  of  potassium  salts,  large  quan- 
tities of  which  are  used  in  the  manufacture  of  fertilizers, 


The  cerargyrite  group  comprises  the  chloride,  bromide  and  iodide  of 
silver.  The  first  two  exist  as  the  minerals  cerargyrite  and  bromargyrite, 
both  of  which  crystallize  in  the  isometric  system.  The  isometric  Agl 
exists  only  above  146°;  below  this  temperature  the  iodide  is  hexagonal. 
The  exhagonal  modification  occurs  as  the  mineral  iodyrite,  which,  of 
course,  is  not  regarded  as  a  member  of  the  cerargyrite  group 


Cerargyrite  (AgCl) 

Cerargynte,  or  horn  silver,  is  an  important  silver  ore  It  is  usually 
associated  with  other  silver  compounds,  the  mixture  being  mined  and 
smelted  without  separation  of  the  components  It  is  usually  recog- 
nizable by  its  waxy,  massive  character 

Silver  chloride  consists  of  24  7  per  cent  chlorine  and  75  3  per  cent 
silver,  but  cerargynte  often  contains,  in  addition  to  its  essential  con- 
stituents, some  mercury,  bromine  and  occasionally  some  iodine  Crystals 
are  rare  They  are  isometric  (hexoctahedral  class),  with  a  cubical  habit, 
their  predominant  forms  being  oo  O  oo  (100),  oo  0(no),  0(in),  20(221) 
and  202(211)  Twins  sometimes  occur  with  0(in)  the  twinning  face 
The  mineral  is  sometimes  found  massive,  embedded  among  other  min- 
erals, but  is  more  frequently  in  crusts  covering  other  substances 

The  fracture  of  cerargynte  is  conchoidal  The  mineral  is  sectile 
Its  hardness  is  i-i  5  and  density  about  5  5  Its  color  is  grayish,  white 
or  yellow,  sometimes  colorless.  On  exposure  to  light  it  turns  violet- 
brown  It  is  transparent  to  translucent  and  its  streak  is  white  It  is  a 
very  poor  conductor  of  electricity  Like  halite  it  is  diathermous  n  for 
sodium,  light  =  2  071. 

In  the  closed  tube  cerargynte  fuses  without  decomposition  On 
charcoal  it  yields  a  metallic  globule  of  silver,  and  when  heated  with  oxide 
of  copper  m  the  blowpipe  flame  it  gives  the  chlorine  reaction  The  min- 
eral is  insoluble  in  water  and  in  nitric  acid  but  is  soluble  in  ammonia,  and 
potassium  cyanide.  When  a  particle  of  the  mineral  is  placed  on  a 
sheet  of  zinc  and  moistened  with  a  drop  of  water,  it  swells,  turns  black 
and  is  finally  reduced  to  metallic  silver,  which,  when  rubbed  by  a  knife 
blade,  exhibits  the  white  luster  of  the  metal. 

Cerargyrite  is  easily  distinguished  from  all  other  minerals,  except 
the  comparatively  rare  bromide  and  iodide,  by  its  physical  properties  and 
by  the  metallic  globule  which  it  yields  on  charcoal 

Syntheses.— Crystals  of  cerargynte  have  been  obtained  by  the  rapid 
evaporation  of  ammoniacal  solutions  of  silver  chloride,  and  by  the  cooling 
of  solutions  of  the  chloride  in  molten  silver  iodide 

Occurrence — The  mineral  occurs  in  the  upper  (oxidized)  portions  of 
veins  of  argentiferous  minerals,  where  it  is  associated  with  native  silver 
and  oxidized  products  of  various  kinds 

Localities.— The  most  important  localities  of  cerargynte  are  in  Peru, 
Chile,  Honduras  and  Mexico,  where  it  is  associated  with  native  silver. 
It  is  also  found  near  Leadville,  Colo*;  near  Austin,  in  the  Comstock 
lode,  Nev.,  and  at  the  Poorman  Mine,  and  in  other  mines  in  Idaho 



and  at  several  places  in  Utah.  Good  crystals  occur  in  the  Poorman 

Extraction  — When  a  silver  ore  consists  essentially  of  cerargynte  the 
metal  may  be  extracted  by  amalgamation  Ores  containing  compara- 
tively small  quantities  of  cerargynte  are  smelted 

Production — The  quantity  of  cerargyrite  mined  cannot  be  safely 
estimated.  As  has  been  stated,  it  is  usually  wrought  with  other  silver 


The  fluorides  are  salts  of  hydrofluoric  acid.  There  are  several 
known  to  occur  as  minerals,  but  only  two,  the  fluoride  of  calcium  and 

FIG  60  —Group  of  Fluonte  Crystals  from  Weardale,  Co.,  Durham,  England     (Foote 

Mineral  Company ) 

the  double  fluorides  of  sodium  and  aluminium  are  of  sufficient  impor- 
tance to  merit  description  here. 

Fluorite  (CaF2) 

Fluorite,  or  fluorspar,  is  the  principal  source  of  fluorine.    It  is  usually 
a  transparent  mineral  that  is  characterized  by  its  fine  color  and  its  hand- 



some  crystals  (Fig  60)  Perhaps  there  is  no  other  mineral  known  that 
can  approach  it  m  the  beauty  of  its  crystal  groups  The  uncrystallized 
fluorite  may  be  massive,  granular  or  fibrous 

Fluonte  is  a  compound  of  Ca  and  F  in  the  proportion  of  48  9  per  cent 
F  and  51  i  per  cent  Ca  Chlorine  is  occasionally  present  in  minute 
quantities,  and  SiCfe,  AkOs  and  Fe20s  are  always  present  A  sample  of 
commercially  prepared  fluonte  from  Marion,  Ky  ,  gave 

94  72 


I    22 


i  82 



The  crystallization  is  isometric  (hexoctrahedral  class),  and  inter- 
penetration  twins  are  frequent     The  principal  forms  observed  are 

FIG  6 1 

FIG  62 

FIG  61  —Crystal  of  Fluonte  with  oo  O  oo  ,  100  (a)  and  «  02,  210  (e). 
FIG  62  — Interpeaetration  Cubes  of  Fluonte,  Twinned  about  O(in) 

0(ui),  oo  O  oo  (100),  oo  02(210)  and  462(421)  (Fig  61),  but  some  crys- 
tals are  highly  modified,  as  many  as  58  forms  having  been  identified  upon 
the  species  The  twins,  with  O(ni)  the  twinning  plane,  are  usually 
interpenetration  cubes,  or  cubes  modified  on  the  corners  by  the  octa- 
hedrons (Fig.  62).  The  mineral  occurs  also  in  granular,  fibrous  and 
earthy  masses. 

The  cleavage  of  fluorite  is  perfect  parallel  to  0(in).  The  mineral 
is  brittle,  its  fracture  is  uneven  or  conchoidal,  its  hardness  is  4  and  its 
density  about  3.2.  It  mdts  at  1387°.  Its  color  is  some  shade  of  yel- 
low, white,  red,  green,  blue  or  purple,  its  luster  vitreous,  and  its  streak 
is  white  Many  specimens  are  transparent,  some  are  only  translucent. 
Most  specimens  phosphoresce  upon  heating  A  vanety  that  exhibits  a 
green  phosphoresence  is  known  as  cfdorophane  The  index  of  refraction 
for  sodium  light  is  1 43385  at  20°.  The  mineral  is  a  nonconductor  of 

The  color  of  the  brightly  tinted  varieties  was  formerly  thought  to  be 
due  to  the  presence  of  minute  traces  of  organic  substance  since  it  is  lost 


or  changed  when  the  mineral  is  heated,  but  recent  observations  of  the 
effect  of  radium  emanations  upon  light-colored  specimens  indicate  a 
deepening  of  their  color  by  an  increase  in  the  depth  of  the  blue  tints. 
This  suggests  that  the  coloring  matter  is  combined  with  the  CaF2-  It 
may  be  a  colloidal  substance 

In  the  closed  tube  fluonte  decrepitates  and  phosphoresces  When 
heated  on  charcoal  it  fuses,  colors  the  flame  yellowish  red  and  yields  an 
enamel-like  residue  which  reacts  alkaline  to  litmus  paper  Its  powder 
treated  with  sulphuric  acid  yields  hydrofluoric  acid  gas  which  etches 
glass.  The  same  effect  is  produced  when  the  powdered  mineral  is  fused 
with  four  times  its  volume  of  acid  potassium  sulphate  (HKSO*)  in  a 
glass  tube  The  walls  of  the  tube  near  the  mixture  become  etched  as 
though  acted  upon  by  a  sand  blast. 

Fluonte  is  easily  distinguished  by  its  cleavage  and  hardness  from 
most  other  minerals  It  is  also  characterized  by  the  possession  of 
fluorine  for  which  it  gives  dear  reactions. 

Syntheses  — Crystals  are  produced  upon  the  cooling  of  a  molten  mix- 
ture of  CaF2  and  the  chlorides  of  the  alkalies,  and  by  heating  amorphous 
CaF2  with  an  alkaline  carbonate  and  a  little  HC1  in  a  closed  tube  at  250°. 

Occurrence,  Localities  and  Origin. — The  mineral  occurs  in  beds,  in 
veins,  often  as  the  gangue  of  metallic  ores  and  as  crystals  on  the  wails 
of  cavities  in  certain  rocks.  It  is  the  gangue  of  the  lead  veins  of  northern 
England  and  elsewhere.  Handsome  crystallized  specimens  come  from 
Cumberland  and  Derbyshire,  England;  Kongsberg,  Norway,  Cornwall, 
Wales,  and  from  the  mines  of  Saxony.  In  the  United  States  the  mineral 
forms  veins  on  Long  Island;  in  Blue  Hill  Bay,  Maine,  at  Putney,  in 
Vermont;  at  Plymouth,  Conn  ;  at  Lockport  and  Macomb,  in  New 
York,  at  Amelia  Court  House,  Va.,  and  abundantly  in  southeastern 
Illinois  and  the  neighboring  portion  of  Kentucky,  where  it  occurs  asso- 
ciated with  zinc  and  lead  ores.  These  last-named  localities,  the  neigh- 
borhood of  Mabon  Harbor,  Nova  Scotia,  and  Thunder  Bay,  Lake 
Superior,  afford  excellent  crystal  groups.  In  nature  fluonte  has  been 
apparently  produced  both  by  crystallization  from  solutions  and  by 
pneumatolytic  processes 

Since  fluorite  is  soluble  in  alkaline  waters,  its  place  in  the  rocks  is  often 
occupied  by  calcite,  quartz  or  other  minerals  that  pseudomorph  it. 

Uses  — The  mineral  is  used  extensively  as  a  flux  in  smelting  iron  and 
other  ores,  in  the  manufacture  of  opalescent  glass,  and  of  the  enamel 
coating  used  on  cooking  utensils,  etc  It  is  also  used  in  the  manufacture 
of  hydrofluoric  acid,  which,  in  turn,  is  employed  in  etching  glass  The 
brighter  colored  varieties  are  employed  as  material  for  vases  and  the 


transparent,  colorless  kinds  are  ground  into  lenses  for  optical  instruments 
The  mineral  is  also  cut  into  cheap  gems,  l:no\vn  according  to  color,  as 
false  topaz,  false  amethyst,  etc  Except  \\hen  used  for  making  lenses  or 
as  a  precious  stone,  fluorite  is  prepared  for  shipment  by  crushing,  wash- 
ing and  screening  A  portion  is  ground 

Production  — The  fluonte  produced  in  the  United  States  is  obtained 
mainly  from  Illinois  and  Kentucky,  though  small  quantities  are  mined 
in  Colorado,  New  Mexico  and  New  Hampshire  The  production  in 
1912  amounted  to  116,545  tons,  valued  at  $769,163.  Of  this,  114,410 
tons  came  from  Illinois  and  Kentucky.  The  imports  were  26,176  tons, 
valued  at  $71,616 


These  double  salts  are  apparently  molecular  compounds,  in  which 
usually  two  chlorides  or  two  fluorides  combine,  as  in  AlFa+3NaF 
Moreover,  one  of  the  members  of  the  combination  of  chlorides  is  nearly 
always  either  the  sodium  or  the  potassium  chloride  The  law  of  this 
combination  is  expressed  by  Professor  Remsen  in  these  words  "  The 
number  of  molecules  of  potassium  or  sodium  chloride  which  combine 
with  another  chloride  is  limited  by  the  number  of  chlorine  atoms  con- 
tamed  m  the  other  chloride  "  Thus,  if  NaCl  makes  double  salts  with 
MC12,  in  which  M  represents  any  bivalent  element,  only  two  are  possible, 
viz-  MCl2+NaCl  and  MCl2+2NaCl  With  MC13  three  double  salts 
with  sodium  may  be  formed,  etc  These  double  salts  are  not  regarded 
as  true  molecular  compounds,  but  they  are  looked  upon  as  compounds 
in  which  Cl  and  F  are  bivalent  like  oxygen 

Carnallite  (KMgCls  6H20) 

Carnallite  may  be  regarded  as  a  hydrated  double  chloride  of  the 
composition  MgCk  KC1  6H2O  with  14  i  per  cent  K,  8  7  per  cent  Mg, 
38  3  per  cent  Cl  and  39  o  per  cent  H20  It  occurs  m  distinct  crys- 
tals but  more  frequently  in  massive  granular  aggregates 

Its  crystallization  is  orthorhombic  (bipyramidal  class),  but  the  habit 
of  its  crystals  is  usually  hexagonal  because  of  the  nearly  equal  develop- 
ment of  pyramids  and  brachydomes.  Its  axial  ratio  is  .5891  i  i  3759. 
Crystals  are  commonly  bounded  by  oo  P(no),  P(in),  JP(ri2),  £P(ii3), 
oo  P  eo  (oio),  2?  a&  (021),  P  56  (on),  |P  oa  (023),  oP(ooi),  and  P  56  (101). 
The  angle  no  A  3 10=61°  2oJ'. 

Carnallite  is  colorless  to  milky  white,  transparent  or  translucent, 
and  has  a  fatty  luster  Many  varieties  appear  red  in  the  hand  specimens 


because  of  the  inclusion  of  numerous  small  plates  of  hematite  or  goethite, 
or  yellow  because  of  inclusions  of  yelkm  liquids  or  tiny  crystals.  The 
mineral  has  a  hardness  of  1-3,  and  a  density  of  1.60  It  possesses  no 
cleavage  but  has  a  conchoidal  fracture  It  is  not  an  electrical  conductor. 
It  is  deliquescent  and  has  a  bitter  taste  Its  indices  of  refraction  for 
sodium  light  are  a=  i  467,  jS=  1.475,  7=  1-494 

Before  the  blowpipe  carnalhte  fuses  easily.  In  the  closed  tube  it 
becomes  turbid  and  gives  off  much  water,  which  is  frequently  accom- 
panied by  the  odor  of  chlorine.  It  melts  in  its  own  water  of  crystalliza- 
tion. When  evaporated  to  dryness  and  heated  by  the  blowpipe  flame 
a  white  mass  results  which  is  strongly  alkaline.  The  mineral  dissolves 
in  water,  forming  a  solution  which  reacts  for  Mg,  K  and  Cl 

Carnalhte  is  easily  recognized  by  its  solubility,  its  bitter  taste  and  the 
reaction  for  chlorine 

Synthesis  — The  mineral  separates  in  measurable  crystals  from  a  solu- 
tion of  MgCl2  and  KC1 

Occurrence  and  Origin — Carnalhte  occurs  hi  beds  associated  with 
sylvite,  halite,  kieserite  (p.  246),  and  other  salts  that  have  been  pre- 
cipitated by  the  evaporation  of  sea  water  or  the  water  of  salt  lakes 

Localities  — It  is  found  in  large  quantity  at  Stassfurt,  Germany,  at 
Kalusz,  in  Galicia  and  near  Maman,  in  Persia 

Uses. — Carnalhte  is  used  as  a  fertilizer  and  as  a  source  of  potash 

Cryolite  (NasAlFe) 

Cryolite  usually  occurs  as  a  fine-grained  granular  white  mass  in 
which  are  often  embedded  crystals  of  light  brown  iron  carbonate  (sider- 
ite).  The  formula  given  above  demands  54  4  per  cent  F,  12  8  per  cent 
Al  and  32.8  per  cent  Na.  Analyses  of  pure  white  specimens  correspond 
veiy  closely  to  this 

The  mineral  is  monoclinic  (prismatic  class),  but  crystals  are  exceed- 
ingly rare  and  when  found  they  have  a  cubical  habit.  Their  axial  ratio 
is  a  :  b  :  ^=.9662  :  i  .  i  3882.  £=89°  49'.  The  principal  forms  are 
ooP(no),  oP(ooi),  Pco(oTo),  —P  00(010)  and  P 06(100),  thus  re- 
sembling the  combination  of  the  cube  and  octahedron.  Twins  are  com- 
mon, with  oo  P(no)  the  twinning  plane 

The  deavage  of  cryolite  is  perfect  parallel  to  oP(coi).  Its  fractine 
is  uneven.  Hardness  is  2  5  and  density  about  3.  Its  color  is  snow-white 
inclining  to  red  and  brown.  Its  luster  is  vitreous  or  greasy  and  the 
mineral  is  translucent  to  transparent  Because  of  its  low  index  of 
refraction,  massive  specimens  suggest  masses  of  wet  snow.  The  re- 


fractive  index  /3  for  sodium  light  is  i  364  It  is  a  nonconductor  of 

Cryolite  is  very  easily  fusible,  small  pieces  melting  even  at  the  low 
temperature  of  a  candle  flame  The  mineral  is  soluble  in  sulphuric  acid 
with  the  evolution  of  HF  When  fused  in  the  closed  tube  with  KHS04 
it  yields  hydrofluoric  acid,  and  -ft  hen  fused  on  charcoal  fluorine  is  evolved 
The  residue  treated  with  Co(NOs)2  and  heated  gives  the  color  reaction 

By  the  aid  of  its  reactions  with  sulphuric  acid,  its  fusibility  and  its 
physical  properties  cryolite  is  easily  distinguished  from  fluonte,  which  it 
most  resembles,  and  from  all  other  minerals. 

Occurrence,  Localities  and  Origin  —The  occurrences  of  cryolite  are 
very  few  It  has  been  found  in  small  quantities  near  Miask  in  the 
Ihnen  Mts,  Russia,  near  Pike's  Peak,  Colo,  and  in  the  Yellowstone 
National  Park.  Its  puncipal  occurrence  is  m  a  great  pegmatitic  vein 
cutting  granite  near  Ivigtut,  Greenland,  whence  all  the  mineral  used 
in  the  arts  is  obtained  The  associates  of  the  cryolite  at  this  place  are 
sidente,  galena,  chalcopynte,  p^nte,  fluonte,  topaz  and  a  few  rare 
minerals  The  vein  is  said  to  be  intrusive  into  the  granite.  It  is 
believed  to  be  a  magmatic  concentration 

Uses. — Cryolite  was  formerly  employed  principally  in  the  manufac- 
ture of  alum  and  of  salts  of  sodium.  At  present  it  is  used  as  a  flux  in 
the  electrolytic  production  of  aluminium,  and  is  employed  in  the  man- 
ufacture of  white  porcelain-like  glass,  and  in  the  process  of  enameling 
iron  The  mineral  is  quarried  in  Greenland  and  imported  into  the 
United  States  to  the  extent  of  about  2,500  tons  annually.  Its  value  is 
about  $25  per  ton. 


The  oxychlorides  are  combinations  of  hydroxides  and  chlorides 
Some  of  them  are  "  double  salts  "  in  the  sense  in  which  this  word  is 
explained  above.  Atacamite  is  a  combination  of  the  oxychlonde 

Cu(OH)Cl  with  the  hydroxide  Cu(OH)2,  or       Ncu  Cu(OH)2. 

Atacamite  (Cu(OH)Cl-Cu(OH)2) 

Atacamite  is  especially  abundant  in  South  America  The  mineral 
is  usually  found  in  crystalline,  fibrous  or  granular  aggregates  of  a  bright 
green  color 

Analyses  of  specimens  from  Australia  and  from  Atacama,  Chile,  yield. 







16  44 

14  67 


12  O2 

99  77 

IS  83 

14  16 

55  7° 

14  31 

IOO  00 

Atacama,  Chile. 

The  formula  lequires  16  6  per  cent  Cl,  14.9  per  cent  Cu,  55  8  per  cent 
CuO  and  12  7  per  cent  EkO. 

The  crystallization  of  atacamite  is  orthorhombic  (bipyramidal  class), 
with  a  :  b  :  £=.6613  :  i :  .7529  Its  crystals  are  usually  slender  prisms 
bounded  by  ooP(no),  ooP£(i2o),  ooPoo  (oio),  P66  (011),  oP(ooi) 
and  P(III),  or  tabular  forms  flattened  m  the  plane  of  the  macropinacoid 
oo  P  56  (100).  Twins  are  common,  with  the  twinning  plane  ooP(no). 

The  cleavage  of  atacamite  is  perfect  parallel  to  oo  P  06  (oio).  Its 
fracture  is  conchoidal.  Its  hardness  is  3-3  5  and  density  about  3  76. 
Pure  atacamite  is  of  some  shade  of  green,  varying  between  bright  shades 
and  emerald.  Its  aggregates  often  contain  red  or  brown  streaks  or 
grains  due  to  the  admixture  of  copper  oxides.  It  is  transparent  to  trans- 
lucent. The  streak  of  the  mineral  is  apple-green  It  is  a  nonconductor 
of  electricity  Its  indices  of  refraction  for  green  light  are  a=i  831, 
0=  1.861,7=1  880 

In  the  closed  tube  atacamite  gives  off  much  water  with  an  acid  reac- 
tion, and  yields  a  gray  sublimate  In  the  oxidizing  flame  it  fuses  and 
tinges  the  flame  azure  blue  (reaction  for  copper  chloride).  It  is  easily 
reduced  to  a  globule  of  copper  on  charcoal  and  is  easily  soluble  in  acids. 

Atacamite  is  readily  distinguished  from  garmerite,  malachite  and 
other  green  minerals  by  its  solubility  in  acids  without  effervescence  and 
by  the  azure  blue  color  it  imparts  to  the  flame. 

Synthes^s. — Crystals  have  been  produced  by  heating  cuprous  oxide 
(CugO)  with  a  solution  of  FeCls,  in  a  closed  tube  at  250°. 

Occurrence,  Localities  and  Origin — The  mineral  is  most  abundant 
along  the  west  side  of  the  Andes  Mountains  in  Chile  and  Bolivia.  It 
occurs  also  in  South  Australia,  in  India,  at  Ambriz,  on  the  west  coast  of 
Afnca,  in  southern  Spain,  in  Cornwall,  where  it  forms  stalactite  tubes, 
in  southern  California,  and  near  Jerome,  Arizona.  It  is  formed  as  the 
result  of  the  alteration  of  other  copper  compounds,  and  is  found  most 
abundantly  in  the  upper  portions  of  copper  veins  Atacamite  changes 
on  exposure  to  the  weather  into  the  carbonate,  malachite,  and  the  sili- 
cate, chrysocolla. 

Uses. — The  mineral  is  an  important  ore  of  copper,  but  it  is  mined 
with  other  compounds  and  consequently  no  records  of  the  quantity 
obtained  are  available. 


THE  oxides  (except  water)  and  the  hydroxides  may  be  regarded  as 
derivatives  of  water,  the  hydrogen  being  replaced  wholly  or  in  part 
by  a  metal.  When  only  part  of  the  hydrogen  is  replaced  an  hydroxide 
results,  when  all  of  the  hydrogen  is  replaced  an  oxide  results  Thus, 
sodium  hydroxide,  NaHO,  may  be  looked  upon  as  HgO,  in  which  Na  has 
replaced  one  atom  of  H,  and  sodium  oxide,  Na20,  as  KfeO  in  which  both 
hydrogen  atoms  have  been  replaced  by  this  element  Ferric  oxide  and 
ferric  hydroxide  bear  these  relations  to  water: 

H-0—  H 

H—  O—  H,    Fe—  O—  Fe,   feme  oxide,    H—  O—  Fe,  ferric  hydroxide 

YFe203        H-0/  Fe(OH)3 

The  oxides  constitute  a  very  important,  though  not  a  large,  class  of 
minerals  Some  of  them  are  among  the  most  abundant  of  all  minerals 
They  are  separated  into  the  following  groups:  Monoxides,  sesqui- 
oxides,  dioxides  and  higher  oxides. 


Ice  (H2O) 

The  properties  of  ice  are  so  well  known  that  they  need  no  special 
description  in  this  place  The  mineral  is  never  pure,  since  it  contains, 
in  all  cases,  admixtures  of  various  soluble  salts.  Its  crystallization  is 
hexagonal  and  probably  trigonal  and  hemimorphic  (ditngonal  pyram- 
idal class).  Crystals  are  often  prismatic,  as  when  ice  forms  the  cover- 
ing of  water  surfaces,  or  the  bodies  known  as  hailstones  In  the  form 
of  snow  the  crystals  are  often  stellate,  or  skeleton  crystals,  and  sometimes 




hollow  prisms     The  principal  forms  observed  on  ice  crystals  are  oP(oooi) 
ooP(ioTo),  |P(iol2),  P(ioTi)  andtfUoli)  (Fig  63). 

The  hardness  of  ice  is  about  1.5  and  its  density  9181  It  is  trans- 
parent and  colorless  except  m  large  masses  when  it  appears  bluish.  Its 
fracture  is  conchoidal  It  possesses  no  distinct  cleavage  Its  fusing 

FlG.  63  — Photographs  of  Snow  Crystals,  .Magnified  about  15  Diameters     (After 

Benttey  and  Perkins ) 

point  is  o°  and  boiling  point  100°.    It  is  a  poor  conductor  of  electricity. 
Its  indices  of  refraction  for  sodium  light  at  8°  are:  «=  1.3090,  €=  1.3133. 


There  are  two  oxides  of  copper,  the  red  cuprous  oxide  (Cu2O)  and 
the  black  cupric  oxide  (CuO).  Both  are  used  as  ores,  the  former  being 
much  more  important  a  source  of  the  metal  than  the  latter 

Cuprite  (Cu2O) 

Cuprite  occurs  in  crystals,  in  granular  and  earthy  aggregates  and 
massive  The  mineral  is  usually  reddish  brown  or  red  and  thus  is  easily 
distinguished  from  most  other  minerals.  Its  composition  when  pure  is 
88.8  per  cent  Cu  and  n  2  per  cent  O. 

In  crystallization  the  mineral  is  isometric,  in  the  gyroidal  hemihedral 
division  of  the  system  (pentagonal  icositetrahedral  dass).  Its  pre- 


dominant  forms  axe  ooOoo(ioo),  0(iu),  ooO(uo),  0002(210), 
202(211),  20(221)  and  301(321),  sometimes  lengthened  out  into 
capillary  crystals,  producing  fibrous  varieties  (var  chdcotr^ch^te). 

The  cleavage  of  cupnte  is  fairly  distinct  parallel  to  O(in)  Its  frac- 
ture is  uneven  or  conchoidal  Its  hardness  is  3  5-4  and  density  about  6 
The  mineral  is  in  some  cases  opaque,  oftener  it  is  translucent  or  even 
transparent  in  very  thin  pieces  By  reflected  light  its  color  is  red, 
brown  and  occasionally  black.  By  transmitted  light  it  is  crimson  When 
gently  heated  transparent  varieties  turn  dark  and  become  opaque,  but 
they  reassume  their  original  appearance  upon  cooling.  Its  streak  is 
brownish  red  and  has  a  brilliant  luster  When  rubbed  it  becomes  yellow 
and  finally  green.  The  luster  of  the  mineral  vanes  between  earthy  and 
almost  vitreous  It  is  a  poor  conductor  of  electricity,  but  its  con- 
ductivity increases  rapidly  with  using  temperature.  Its  refractive  index 
for  yellow  light =  2.705 

In  the  blowpipe  flame  cuprite  fuses  and  colors  the  mantle  of  the 
flame  green  If  moistened  with  hydrochloric  acid  before  heating  the 
flame  becomes  a  brilliant  azure  blue.  On  charcoal  the  mineral  first 
fuses  and  then  is  reduced  to  a  globule  of  metallic  copper.  It  dissolves  in 
strong  hydrochloric  acid,  forming  a  solution  which,  when  cooled  and 
diluted  with  cold  water,  yields  a  white  precipitate  of  cuprous  chloride 

Cupnte  may  easily  be  distinguished  from  other  minerals  possessing 
a  red  streak  by  the  reaction  for  copper — such  as  the  production  of  a 
metal  globule  on  charcoal,  and  the  formation  of  cuprous  chloride  in  con- 
centrated hydrochloric  acid  solutions  by  the  addition  of  water.  More- 
over, the  mineral  is  softer  than  hematite  and  harder  than  reaglar,  cin- 
nabar and  proitsttte. 

Cuprite  suffers  alteration  very  readily.  It  may  be  reduced  to  native 
copper,  in  which  case  the  copper  pseudomorpbs  the  cuprite,  or,  on  ex- 
posure to  the  air  it  may  be  changed  into  the  carbonate,  malachite, 
pseudomorphs  of  which  after  cupnte  are  common. 

Syntheses — Crystals  of  cupnte  have  frequently  been  observed  on 
copper  utensils  and  coins  that  had  been  buried  for  long  periods  of  time. 
Crystals  have  also  been  obtained  by  long-continued  action  of  NHs  upon 
a  mixture  of  solutions  of  the  sulphates  of  iron  and  copper,  and  by  heating 
a  solution  of  copper  sulphate  and  ammonia  with  iron  wire  in  a  dosed  tube 

Occurrence^  Origin  and  Localities — Cuprite  often  occurs  as  well 
defined  crystals  embedded  in  certain  sedimentary  rocks  in  the  upper, 
oxidized  portions  of  copper  veins,  and  in  masses  m  the  midst  of  other 
copper  ores,  from  which  it  was  produced  by  oxidation  processes*  It  is 

OXIDES  149 

found  as  crystals  in  Thuringia,  in  Tuscany,  on  the  island  of  Elba,  in 
Cornwall,  Eng ,  at  Chessy,  France,  and  near  Coquimbo,  in  Chile. 
In  Chile,  m  Peru,  and  in  Bolivia  it  exists  in  great  masses 

In  the  United  States  it  occurs  at  Cornwall,  Lebanon  Co  ,  Penn.  It 
is  also  found  associated  with  the  native  copper  on  Keweenaw  Point, 
Mich  ,  at  the  copper  mines  in  St.  Genevieve  Co ,  Mo  ;  at  Bisbee  and 
at  other  places  in  Arizona  The  fibrous  vanety  known  as  chalcoinchite 
is  beautifully  developed  at  Morenci  in  the  same  State. 

Uses  —Cuprite  is  mined  with  other  copper  compounds  as  an  ore  of 

Melaconite,  or  Tenorite  (CuO) 

Melaconite,  or  tenonte,  is  less  common  than  cuprite.  It  usually 
occurs  in  massive  forms  or  in  earthy  masses  Crystals  are  rare  Its 
composition  is  79  8  per  cent  Cu  and  20  2  per  cent  0. 

In  crystallization  melacomte  is  tnchnic  with  a  monochnic  habit. 
Its  axial  ratio  is  a :  b  :  c=i  4902  :  i :  1 3604  and  £=99°  32'.  The 
angles  a  and  7  are  both  90°,  but  the  optical  properties  of  the  crystals 
proclaim  their  tnchnic  symmetry. 

The  mineral  possesses  an  easy  cleavage  parallel  to  oP(ooi).  Its  frac- 
ture is  conchoidal  and  uneven,  its  hardness  3  to  4  and  density  about  6. 
When  it  occurs  in  thin  scales  its  color  is  yellowish  brown  or  iron  gray. 
When  massive  or  pulverulent  it  is  dull  black.  Its  streak  is  black,  chang- 
ing to  green  when  rubbed.  Its  refractive  index  for  red  light  is  2  63. 
It  is  a  nonconductor  of  electricity. 

The  chemical  reactions  of  melaconite  are  precisely  like  those  of  cu- 
pnte,  with  the  exception  that  the  mineral  is  infusible. 

Melaconite  is  distinguished  from  the  black  minerals  that  contain  no 
copper  by  its  reaction  for  this  metal  It  is  distinguished  from  covelhte 
and  other  dark-colored  sulphides  containing  copper  by  its  failure  to  give 
the  sulphur  reaction. 

Syntheses  — Crystals  of  melaconite  have  been  found  in  the  flues  of 
furnaces  in  which  copper  compounds  and  moist  NaCl  are  being  treated. 
They  have  also  been  obtained  by  the  decomposition  of  CuCk  by  water 

Occurrence,  Localities  and  Origin.— The  mineral  usually  occurs  associ- 
ated with  other  ores  of  copper,  from  which  it  has  been  formed,  in  part 
at  least,  by  decomposition.  It  is  mined  with  these  as  jmt  ore.  Thin 
scales  are  found  on  the  lava  of  Vesuvius,  where  it  must  have  been  f  onned 
by  sublimation.  Masses  occur  at  the  copper  mines  of  Ducktowu,  Temi. 


Zincite  (ZnO) 

Zincite  is  the  only  oxide  of  the  zinc  group  of  elements  known  It  is 
rarely  found  in  crystals  It  usually  occurs  m  massive  forms  associated 
with  other  zinc  compounds. 

Pure  zmcite  is  a  compound  containing  80  3  per  cent  Zn  and  19  7  per 
cent  0,  Since,  however,  the  mineral  is  frequently  admixed  with  man- 
ganese compounds  it  often  contains  also  some  manganese  and  a  little 
iron.  A  specimen  from  Sterling  Hill,  N  J , 
gave  98  28  per  cent  ZnO,  6  50  per  cent  MnO 
and  44  per  cent  Fe20g 

Natural  crystals  of  zmcite  are  very  rare 
From  a  study  of  artificial  crystals  it  is  known 
that  the  mineral  is  hexagonal  and  hemimorphic 
(dihexagonal  pyramidal  class).    The  principal 
forms  observed  are    ooP(ioTo),     ooP2(ii2o), 
oP(oooi),  P(ioTi),  P2(ii22)  and  various  other 
Fro.  64  —Zincite  Crystal    pyramids  of  the  ist  and  2d  orders     Their  habit 
with  oop,    iolo  (m).    1S  hemimorphic  with  P(iori)  and  oP(oooi)  at 
p,  roll  (p)  and  oP,    ^  oppOSite  ends  of  a  short  columnar  crystal 
0001  W  (Fig.  64) 

The  cleavage  of  ^incite  is  perfect  parallel  to  oP(oooi)  Its  fracture 
is  conchoidal,  its  hardness  4-4  5  and  density  about  5  8  Although  color- 
less varieties  are  known,  the  mineral  is  nearly  always  deep  red  or  orange- 
yellow,  due  most  probably  to  the  manganese  present  in  it  The  streak 
of  the  red  varieties  is  orange- yellow.  Its  indices  of  refraction  are 
about  2  The  mineral  is  a  conductor  of  electricity. 

When  heated  in  the  closed  tube  the  common  variety  of  zmcite 
blackens,  but  it  resumes  its  original  color  on  cooling  With  the  borax 
bead  it  gives  the  manganese  reaction  Heated  on  charcoal  it  coats  the 
coal  with  a  white  film,  which,  when  moistened  with  cobalt  solution  and 
heated  again  with  the  oxidizing  flame  of  the  blowpipe,  turns  green  The 
mineral  dissolves  in  acids 

When  exposed  to  the  atmosphere  zmcite  undergoes  slow  decomposi- 
tion to  zinc  carbonate 

Syntheses  — Zinc  oxide  crystals  are  frequent  products  of  the  roasting 
of  zinc  ores  in  ovens  They  have  also  been  produced  by  the  action  of 
zinc  chloride  vapor  upon  lime  and  by  the  action  of  water  upon  zinc 
chloride  at  a  red  heat. 

Occurrence  and  Locafofoes  — The  mineral  occurs  only  in  a  few  places 
It  is  found  with  other  zinc  and  manganese  minerals  near  Ogdensburg, 

OXIDES  151 

and  at  Franklin  Furnace,  m  Sussex  Co ,  N  J ,  m  the  form  of  great 
layers  in  marble,  that  are  bent  into  troughs  The  lajers  are  probably 
veins  that  were  filled  from  below  by  emanations  from  a  great  underground 
reservoir  of  igneous  rock 

Uses  — Most  of  the  zmcite  produced  in  the  United  States  is  used  in 
the  manufacture  of  zinc  oxide  The  ore,  which  consists  of  a  mixture  of 
zincite,  franklimte  (see  p  199),  and  willemite  (see  p  306),  is  crushed 
and  separated  into  its  component  parts  by  mechanical  processes  The 
separated  zmcite  is  then  mixed  with  coal  and  roasted  The  zinc  oxide 
is  volatilized  and  is  caught  m  tubes  composed  of  bagging.  The  willemite 
and  franklimte  are  smelted  to  metallic  zinc  and  the  residues  are  used  m 
the  manufacture  of  spiegeleisen 

Production  — Formerly  this  mineral,  together  TMth  the  silicate  found 
associated  with  it  in  New  Jersey,  constituted  the  most  important  source 
of  zinc  in  this  country  At  present  most  of  the  metal  is  obtained  from 
sphalerite  Of  the  380,000  tons  of  zinc  in  spelter  and  zinc  compounds 
produced  in  the  United  States  during  1912  about  69,760  tons  were 
made  from  zmcite  and  the  ores  associated  with  it.  This  had  an  esti- 
mated value  of  $9,626,991. 


The  sesquioxides  (R20s)  include  a  few  compounds  of  the  nonmetals 
that  are  comparatively  rare  and  a  group  of  metallic  compounds  that 
includes  two  minerals  of  great  economic  importance.  One  of  these, 
hematite  (FeaOa),  is  the  most  valuable  of  the  iron  ores 


The  only  group  of  the  nonmetallic  sesquioxides  that  need  be  referred 
to  in  this  place  comprises  those  of  arsenic  and  antimony.  This  is  an 
isodimoiphous  group  including  four  minerals. 

Isometric  Monochmc 

Arsenohte  As20s  Claudetite 

Senarmoutote  Sb20s  Valenttmte 

All  the  minerals  of  the  group  are  comparatively  rare.  The  isometric 
forms  occur  in  well  developed  octahedrons  and  in  crusts  covering  other 
minerals  They  are  also  found  in  earthy  masses.  It  is  probable  that  at 
high  temperatures  the  isometric  forms  pass  over  into  the  monodinic 
modifications,  as  some  of  the  latter  have  been  abserved  to  consist  of 
aggregates  of  tiny  octahedrons.  Crystals  of  daudetite  are  distinctly 


monoclinic,  but  they  are  so  thinned  as  to  possess  an  orthorhombic 
habit  Valentmite  crystals,  on  the  contrary,  appear  to  be  plainly 
orthorhombic,  but  their  apparent  orthorhombic  symmetry  may  be 
due  to  submicroscopic  twinning  of  the  same  character  as  that  in 
claudetite,  but  which  in  the  latter  mineral  is  macroscopic 

All  four  minerals  occur  as  weathered  products  of  compounds  contain- 
ing As  or  Sb  They  give  the  usual  blowpipe  reactions  for  As  or  Sb 
In  the  closed  tube  they  melt  and  sublime 

Arsenolite  (As2Os)  is  colorless  or  white  Its  specific  gravity  is  3,7 
and  refractive  index  for  sodium  light  =  i  755  It  usually  occurs  in  octa- 
hedrons, or  m  combinations  of  0(in)  and  ooO(no),  but  these  when 
viewed  in  polarized  light  are  often  seen  to  be  amsotropic  The  mineral  is 
found  also  in  aggregates  of  hair-like  crystals  with  a  hardness  of  i  2  It  is 
soluble  in  hot  water,  yielding  a  solution  with  a  sweetish  taste 

Senarmonite  (SbgOs)  is  gray  or  white  Its  density  is  5  2  and 
n=2  087  for  yellow  light  Its  octahedral  crystals  are  also  often  aniso- 
tropic,  its  hardness=2  It  is  soluble  in  hot  HC1  but  is  only  very 
slightly  soluble  in  water  When  heated  it  turns  yellow,  but  becomes 
white  again  upon  cooling 

Claudetite  (As2Os)  is  monochmc  prismatic,  with  a  :  b  :  c=  4040  :  i 

:  3445  and  /3=86°  03'     Its  white  crystals  are  usually  tabular  parallel 

to  oo  P  ao  (oio)  and  are  twinned,  with  oo  P  56  (100)  the  twinning  plane 

Their  cleavage  is  parallel  to  oo  P  o>  (oio)  and  their  density  is  4  15 

H=  2.5     The  mineral  is  an  electrical  nonconductor 

Valentinite  (Sb2Os)  is  apparently  orthorhombic  bipyramidal  (pos- 
sibly monoclimc  prismatic)  with  a  :  b  :  c=  3914  •  i  3367  Its  crystals 
are  tabular  or  columnar  in  habit  and  are  very  complex  The  mineral  is 
found  also  in  radial  groups  of  acicular  crystals  and  m  granular  and 
dense  masses  Its  color  is  white,  pink,  gray  or  brown,  and  streak 
white  Its  density  is  5  77  and  hardness  2  5-3.  It  is  insoluble  in  HC1 
It  is  a  nonconductor  of  electricity 


The  sesquioxides  of  aluminium  and  iron  constitute  an  isomorphous 
group  crystallizing  in  the  rhombohedral  division  of  the  hexagonal  sys- 
tem (ditngonal  scalenohedral  class)  Both  the  aluminium  and  iron 
compounds,  corundum  and  hematite^  are  of  great  economic  importance 



Hematite  (Fe20a) 

Hematite  is  one  of  the  most  important  minerals,  if  not  the  most 
important  one,  from  the  economic  standpoint,  smce  it  is  the  most  val- 
uable of  all  the  iron  ores  It  is  known  by  its  dark  color  and  its  red 
powder  It  occurs  in  black,  glistening  crystals,  in  yellow,  brown  or  red 
earthy  masses,  in  granular  and  micaceous  aggregates  and  in  botiyoidal 
and  stalactitic  forms 

Chemically,  the  mineral  is  Fe20a  corresponding  to  30  per  cent  0  and 
70  per  cent  Fe.  In  addition  to  these  constituents,  hematite  often  con- 
tains some  magnesium  and  some  titanium.  By  increase  in  the  latter 
element  it  passes  into  a  mineral  which  has  not  been  distinguished  from 
ilmenite  (see  p  462) 

The  habit  of  hematite  crystals  is  nearly  always  rhombohedraL 

FIG*  65— Hematite  Crystals  with  R,  loTi  (r),  |P2,  2243  (*),  JR  1014  («),  oop2l 
1 1 20  (0)  and  oR,  oooi  (c) 

Their  axial  ratio  is  a :  c=i  :  1.3658,  and  the  predominant  forms  are 
R(ioTi),  iR(iol4),  ^2(2243),  the  prisms  oo  P(ioTo)  and  ooP2(ii2o) 
and  often  the  basal  plane  (Fig.  65)  In  addition,  about  no  other  forms 
have  been  identified  The  crystals  are  often  tabular,  and  sometimes 
are  grouped  into  aggregates  resembling  rosettes.  In  many  cases  the 
terminal  faces  are  rounded  A  parting  is  often  observed  parallel  to 
the  basal  plane,  due  to  the  occunence  of  the  mineral  in  aggregates  in 
which  each  crystal  is  tabular. 

Hematite  has  no  well  defined  cleavage  Its  fracture  is  conchoidd  or 
earthy.  Its  crystals  are  black,  glistening  and  opaque,  except  in  very 
small  splinters  These  are  red  and  transparent  or  translucent.  Earthy 
varieties  are  red.  The  streak  of  all  varieties  is  brownish  red  or  cherry- 
red.  The  hardness  of  the  crystallised  hematite  is  5.5-6.5  aad  its  density 
about  5.2.  It  is  a  good  conductor  of  electricity.  Its  refractive  indices 
are:  60=3.22,  6=2.94  for  yellow  light. 

The  mineral  is  infusible  before  the  blowpipe.  In  the  reducing  flame 
on  charcoal  it  becomes  magnetic,  and  when  heated  with  soda  it  is  reduced 
to  a  magnetic  metallic  powder  It  is  soluble  IB  strong  hydrochloric  acid. 


The  crystalline  and  earthy  aggregates  of  hematite  to  which  distinct 
names  have  been  given  are 

Specular,  when  the  aggregate  consists  of  grains  with  a  glistening, 
metallic  luster,  like  the  luster  of  the  crystals  When  the  grains  are  thin 
tabular  the  aggregate  is  said  to  be  micaceous 

Columnar  or  fibrous,  when  in  fibrous  masses  The  color  is  usually 
brownish  red  and  the  luster  dull  The  botryoidal,  stalactic  and  various 
imitative  forms  belong  here  Red  hematite  is  a  compact  red  variety  in 
which  the  fibrous  structure  is  not  very  pronounced 

Red  ocher  is  a  red  earthy  hematite  mixed  with  more  or  less  clay  and 
other  impurities 

Clay  ironstone  is  a  hard  brownish  or  reddish  variety  with  a  dull  luster 
It  is  usually  a  mixture  of  hematite  with  sand  or  clay 

Oolitic  ore  is  a  red  variety  composed  of  compacted  spherical  or  nearly 
spherical  grams  that  have  a  concentric  structure 

Fossil  ore  differs  from  oolitic  ere  mainly  in  the  fact  that  there  are 
present  in  it  small  shells  and  fragments  of  shells  that  are  now  composed 
entirely  of  hematite 

Martite  is  a  pseudomorph  of  hematite  after  magnetite. 

Hematite  is  distinguished  from  all  other  minerals  by  its  red  powder 
and  its  magnetism  after  roasting 

Syntheses  — Crystals  of  hematite  are  obtained  by  the  action  of  steam 
on  ferric  chloride  at  red  heat,  by  heating  ferric  hydroxide  with  water 
containing  a  trace  of  NH*F  to  250°  in  a  closed  tube,  and  by  cooling  a 
solution  of  Fe20s  in  molten  borax  or  halite 

Occurrence  and  Origin — Hematite  is  found  in  beds  with  rocks  of 
nearly  all  ages  It  occurs  also  as  a  deposit  on  the  bottoms  of  marshy 
ponds,  and  m  small  grams  m  the  rocks  around  volcanic  vents  The 
crystallized  variety  is  often  deposited  on  the  sides  of  clefts  in  rocks  near 
volcanoes  and  on  the  sides  of  certain  veins  It  is  produced  by  sublima- 
tion, by  sedimentation  and  by  metasomatic  processes 

Localities  —Handsome  crystals  occur  on  the  island  of  Elba,  near 
Limoges  in  France,  m  and  on  the  lavas  of  Vesuvius  and  Etna,  at  many 
places  in  Switzerland,  Sweden,  etc ,  and  at  many  in  the  United  States 

Beds  of  great  economic  importance  occur  m  the  Gogebic,  Menommee 
and  Marquette  districts  in  Michigan;  m  the  Mesabe  and  Vermilion 
districts  in  Minnesota,  m  the  Pilot  Knob  and  Iron  Mountain  districts 
in  Missouri,  and  in  the  southern  Appalachians,  especially  m  Alabama 

Uses. — In  addition  to  its  use  as  an  ore  the  fibrous  variety  of  hematite 
is  sometimes  cut  into  balls  and  cubes  to  be  worn  as  jewelry.  The  earthy 
varieties  are  ground  and  employed  in  the  manufacture  of  a  dark  red 

OXIDES  155 

paint  such  as  is  used  on  freight  cars,  and  the  ponder  of  some  of  the  mass- 
ive forms  is  used  as  a  polishing  ponder 

Prodtiction.—Most  of  the  iron  ore  produced  in  the  United  States  is 
hematite,  and  by  far  the  greater  proportion  of  it  comes  from  the  Lake 
Superior  region  The  statistics  for  191  2  follow 


Hematite            Other  Iron  Ores  Total 

Minnesota  .....    34j43i,o°o  .  .  34,431,000 

Michigan  .....          11,191,000  11,191,000 

Alabama  .   .        .    3,814,000  749,ooo  4,563,000 

New  York  .                 106,327  1,110,000  1,216,327 

Wisconsin  860,000  860,000 

Tennessee.  246,000  171,000  417,000 

Total  in  U  S  .                    51,345,782  3,804,365  55,150,147 

The  total  production  in  1912  was  valued  at  about  $104,000,000 

Corundum  is  the  hardest  mineral  known,  with  the  exception  of  dia- 
mond In  consequence  of  its  great  hardness  an  impure  variety  is  used 
as  an  abrading  agent  under  the  name  of  emery.  It  is  also  one  of  the 
most  valuable  of  the  gem  minerals  It  occurs  as  crystals  and  in  granular 

The  mineral  is  nearly  always  a  practically  pure  oxide  of  aluminium  of 
the  composition  AkOs,  in  which  there  are  52  9  per  cent  Al  and  47  i  per 
cent  O  The  impure  varieties  usually  contain  some  iron,  mainly  as  an 
admixture  in  the  form  of  magnetite 

The  axial  ratio  of  corundum  crystals  is  i  :  i  36  The  forms  are 
usually  simple  pyramids,  among  which  |P2(2243)  and  |P2(44S3) 
are  the  most  common  (Fig.  66),  and  the  prism  oo  P2(ii2o)  The  basal 
plane  is  also  common  (Fig  67).  Many  crystals  consist  of  a  series  of 
steep  prisms  and  the  basal  plane,  with  a  habit  that  may  be  described  as 
barrel-shaped  (Fig  68)  The  crystals  are  often  rough  with  rounded 
edges  The  prismatic  and  pyramidal  faces  are  usually  striated  hori- 
zontally, and  the  basal  plane  by  lines  radiating  from  the  center 

All  corundum  crystals  are  characterized  by  a  parting  parallel  to  the 
basal  plane,  and  often  by  a  cleavage  parallel  to  the  rhoinbohedron,  due 
to  the  presence  of  lamellae  twinned  parallel  to  R(ioli).  The  fracture 
o£  the  mineral  is  conchoidal  or  uneven.  Its  density  is  about  4  and  its 



hardness  9  The  mineral  possesses  a  vitreous  to  adamantine  luster  It 
is  transparent  or  translucent  Its  streak  is  uncolored  Its  color  varies 
from  white,  through  gray  to  vanous  shades  of  red,  yellow,  or  blue 
The  blue  varieties  are  pleochroic  in  blue  and  greenish  blue  shades  The 
mineral  is  a  nonconductor  of  electricity.  Its  refractive  indices  for 
yellow  light  are  w=i  7690,  €=i  7598. 

Three  varieties  of  corundum  are  recognized  in  the  arts:  Sapphire, 
corundum  and  emery 

Sapphire  is  the  generic  name  for  the  finely  colored,  transparent  or 
translucent  varieties  that  are  used  as  gems,  watch  jewels,  meter  bearings, 
etc.  The  sapphires  are  divided  by  the  jewelers  into  sapphires,  possessing 

FIG  66 

FIG  67 

FIG  68 

FIG  66  — Corundum  Crystal  with  |P2,  4483  (u) 

Fee.  67— Corundum  Crystal  with  R,  loYi  (r),   °oPs,  1120  (a),  and  oR,  oooi  (c) 
FIG.  68  — Corundum  Crystal     Form  a,  v  and  c  as  in  previous  figures     Also  £P2, 
2243  (n)  and  —  2R,  0221  ($) 

a  blue  color,  rubies,  possessing  a  red  shade,  Oriental  topazes,  Oriental 
emeralds  and  Oriental  amethysts  having  respectively  yellow,  green  and 
purple  tints. 

Corundum  is  the  name  given  to  dull  colored  varieties  that  are  ground 
and  used  as  polishing  and  cutting  materials 

Emery  is  an  impure  granular  corundum,  or  a  mixture  of  corundum 
with  magnetite  (FeaO^)  and  other  dark  colored  minerals  Emery,  like 
corundum,  is  used  as  an  abrasive.  It  is  less  valuable  than  corundum 
powder  because  it  contains  a  large  proportion  of  comparatively  soft 

Powdered  corundum  when  heated  for  a  long  time  with  a  few  drops  of 
cobalt  nitrate  solution  assumes  a  blue  color  The  mineral  gives  no 
definite  reaction  with  the  beads  It  is  infusible  and  insoluble.  It  is 

OXIDES  157 

most  easily  recognized  by  its  hardness     The  mineral  alters  to  spinel 
(p   196)  and  to  fibrous  and  platy  aluminous  silicates 

Syntheses  —Corundum  crystals  have  been  produced  artificially  in 
many  different  ways,  but  only  recently  has  the  manufacture  of  the  gem 
variety  been  accomplished  on  a  commercial  scale  Amorphous  Al2Cs 
dissolves  in  melted  sodium  sulphide  and  crystallizes  from  the  glowing 
mass  at  a  red  heat  By  melting  Al20s  in  a  mass  of  some  fluoride  and. 
potassium  carbonate  containing  a  little  chromium,  and  using~compara- 
tively  large  quantities  of  material,  violet  and  blue  rubies  were  obtained 
by  Fremy  and  Verneuil  Rubies  are  also  produced  by  melting  AfaOs 
and  a  little  C^Os  for  several  minutes  at  a  temperature  of  2250°  C  in 
an  electric  oven 

In  recent  years  reconstructed  rubies  have  become  a  recognized  article 
of  commerce  These  are  crystalline  drops  of  ruby  material  made  by 
melting  tiny  splinters  and  crystals  of  the  mineral  in  an  electric  arc 

Alundum  is  an  artificial  corundum  made  by  subjecting  the  aluminium 
hydroxide,  bauxite,  to  an  intense  heat  (5ooo°-6ooo°)  m  an  electric 

Occurrence  and  Origin  — Corundum  usually  occupies  veins  in  crys- 
talline rocks  or  is  embedded  in  basic  intrusive  rocks  and  in  granular 
limestone  The  sapphire  varieties  are  also  often  found  as  partially 
rounded  crystals  in  the  sands  of  brook  beds  The  varieties  found  in 
igneous  rocks  are  primary  crystallizations  from  the  magmas  producing 
the  rocks.  The  varieties  in  limestones  are  the  result  of  metamorphic 

Localities — Sapphires  are  obtained  mainly  from  the  limestone  of 
Upper  Burma  They  are  known  also  to  occur  in  Afghanistan,  in  Kash- 
mir and  in  Ceylon  They  are  occasionally  found  in  the  diamond-bearing 
gravels  of  New  South  Wales  and  in  the  bed  of  the  Missouri  River,  near 
Helena,  Montana  In  the  United  States  sapphire  is  mined  near  the 
Judith  River  in  Fergus  Co  ,  and  in  Rock  Creek  in  Granite  Co.,  Mont., 
where  it  occurs  in  a  dike  of  the  dark  igneous  rock  known  as  monduquite, 
and  is  washed  from  the  placers  of  three  streams  in  the  same  State.  The 
only  southern  mines  that  have  produced  gem  material  are  at  Franklin 
and  Culsagee,  N.  C  ,  and  from  these  not  any  great  quantity  of  stones  of 
gem  quality  have  been  taken 

The  largest  sapphire  crystal  ever  found  was  taken,  however,  from 
one  of  them  It  weighs  312  Ib ,  is  blue,  but  opaque.  From  one  of 
these  mines,  also,  came  the  finest  specimen  cf  green  sapphire  (Oriental 
emerald)  ever  found 

Corundum  in  commercial  quantities  occurs  on  the  coast  of  Malabar, 


m  Siam,  near  Canton,  China,  and  in  southeastern  Ontario,  Canada. 
Emery  is  obtained  from  several  of  the  Grecian  Islands,  more  particularly 
Naxos,  and  from  Asia  Minor  It  is  mined  in  the  United  States  at  Chester, 
Mass,  and  at  Peekskill,  N  Y  Crystallized  corundum  occurs  near 
Litdxfield,  Conn  ,  at  Greenwood,  Maine,  at  Warwick  and  Amity,  N  Y  , 
at  Mineral  Hill,  Penn  ,  m  Patrick  Co  ,  Va  ,  at  Corundum  Hill  and  at 
Laurel  Creek,  Macon  Co.,  N  C ,  and  at  \  anous  points  in  Georgia,  at 
all  of  which  places  it  has  been  mined  In  all  the  localities  within  the 
United  States  the  corundum  occurs  on  the  peripheries  of  masses  of 
pendotite  (ohvine  rocks) 

Uses  — Corundum,  emery  and  alundum,  after  crushing  and  washing, 
are  used  as  abrasives  and  m  the  manufacture  of  cutting  wheels. 

Production. — The  amount  of  sapphire  produced  in  the  United  States 
m  1912  was  valued  at  $195,505  Most  of  it  was  used  for  mechanical 
purposes,  but  384,000  carats  were  used  as  gem  material 

Most  of  the  corundum  used  in  the  United  States  is  imported  from 
Canada,  where  it  occurs  in  Hakburton,  Renfrew  and  neighboring  coun- 
ties in  Ontario,  as  crystals  scattered  through  the  coarse-grained  crys- 
talline rocks  known  as  syenite,  nephelme  syenite  and  anorthosite 

Most  of  the  emery  is  also  imported  Only  992  tons  with  a  value 
of  $6,652  were  mined  in  1912  The  imports  of  corundum  and  emery 
were  valued  at  $501,725,  but  the  importation  of  these  substances  is 
gradually  diminishing  because  of  the  rapid  increase  in  the  amounts 
of  alundum  and  carborundum  manufactured  In  1912  the  production 
of  alundum  reached  13,300,000  Ib  valued  at  $796,000, 



There  are  but  few  dioxides  of  the  nonmetals  that  occur  as  minerals, 
and  only  one  of  these,  quartz,  is  abundant 


Silica  (SiOa)  occurs  in  nature  in  four  or  five  important  modifica- 
tions as  follows. 

a  Qmrtz,  tngonal-trapezohedral  class,  below  575°. 

j8  Quartz,  hexagonal-trapezohedral  class,  above  575°  and  below  870° 

Tridymite,  rhombic  bipyramidal,  pseudohexagonal  habit.  Hex- 
agonal above  117°. 

Cristobdite,  tetragonal  system,  pseudocubic  habit  Isometric  above 



Chalcedony  is  regarded  by  many  mineralogists  as  a  form  of  quartz, 
but  its  index  of  refraction  for  red  light  is  n=i  537,  which  is  noticeably 
lower  than  that  of  either  ray  in  quartz,  which  is  ««i  5390,  e=i  5480 
for  the  same  color  Its  hardness  also  is  a  little  less  than  that  of  quartz. 
Some  mineralogists  believe  that  all  of  these  properties  may  be  explained 
on  the  assumption  that  the  mineral  is  a  mass  of  fine  quartz  fibers,  perhaps 
mixed  with  other  substances,  but  those  \vho  have  investigated  it  by 
high  temperature  methods  are  inclined  to  regard  it  as  a  distinct  mineral 

Quartz  (Si02) 

Quartz  vies  with  calcite  for  the  commanding  position  among  the 
minerals  It  is  very  abundant,  and  appears  under  a  great  variety  of 

FIG  69 

FIG  70. 

FEG  69 — Quartz  Crystal  Exhibiting  Rhombohedral  Symmetry     R,  loir  (r),  — R, 

oili  (s)  and  °°  R,  loTb  (m) 

FIG  70  — Ideal  (A)  and  Distorted  (B)  Quartz  Crystals  Bounded  by  same  Forms  as 

m  Fig  69 

forms  Often  it  occurs  in  distinct  crystals  At  other  times  it  appears 
as  grains  without  distinct  crystal  forms,  and  again  it  constitutes  great 
massive  deposits 

Pure  quartz  consists  of  46  7  per  cent  Si  and  53.3  per  cent  (X  Mass- 
ive varieties  often  contain,  in  addition,  some  opal  (Si(OH)4),  and  traces 
of  iron,  calcite  (CaCOs),  clay,  and  other  impurities 

The  crystallization  of  quartz  is  in  the  trapezohedral  tetartohedral 
division  of  the  hexagonal  system  (trigonaUrapezohedral  class),  at  tem- 
peratures below  575°.  When  formed  above  this  temperature  its  sym- 
metry is  hexagonal  trapezohedral  (hemihedral).  The  former  is  known  as 
a.  quartz,  and  the  latter  as  jS  quartz.  They  readily  pass  one  into  the 
other  at  the  stated  temperature.  The  axial  ratio  is  i :  i.i.  The  prin- 

_  _  —        2P2        — 

cipal  forms  observed  are  +R(ioii),  -R(om),  oo  R(ioio),  — (1121), 



(Fig  74)  and  a  series  of  steep  rhombohedrons  and  trapezo- 
hedrons     Although  these  may  all  be  tetartohedral  since  t  he  geometrical 

FIG  71  — Etch  Figures  on  Two  Quartz  Crystals  of  the  Same  Form,  Illustrating  Dif- 
ferences in  Symmetry  \  Right-Hand  Crystal  B  Left-Hand  Crystal 
(After  Penfidd ) 

FIG   72 — Group  of  Quartz  Crystals  with  Distorted  Rhombohedral  Faces     (Foote 

Mineral  Company ) 

forms  of  the  first  four  are  not  distinguishable  from  the  corresponding 
hemihedral  ones,  the  crystals  possess  a  rhombohedral  symmetry  (Fig. 
69).  The  angle  ioTiA"iioi  =  850  46' 



Often  the  +R  and  the  -R  faces  are  equslly  de\  eloped  so  that  they 
appear  to  belong  to  the  hexagonal  pyramid  P  (Fig  yoA)  Their  true 
character,  ho\\ever,  is  clearly  brought  out  by  etching,  when  figures  are 
produced  on  the  +R  and  the  -R  that  are  differently  situated  with 
respect  to  the  edges  of  the  faces  (Fig  71)  On  the  other  hand,  on  many 
crystals  some  of  the  R  faces  are  very  much  enlarged  at  the  expense  of 
the  others  (Fig  72) 

The  crystals  are  commonly  pnsmatic     Often  they  are  so  dis- 

FIG  73  FIG  74 

FIG  73  —  Tapenng  Quartz  Crystal  with  Rhombohedral  Symmetry     \  Combination 

of  r,  z,  m  and  Two  Steep  Rhombohedrons     B  Cross-section  near  Top. 
FIG   74  —  Quartz  Crystals  Containing  ooR,  iolo  (m),  R,  loll  (r),  —  R,  oiTi  (s), 

),  —  r,  510*1  (*) 

and  —  /,  sin 



),  —  -/,  sT6"i  (*)  on  A,  and  —  r,  1121 

2  2 

torted  that  it  is  difficult  to  detect  the  position  of  the  c  axis  (Fig 
708)  The  stnations  on  oo  R(ioTb)  are,  however,  always  parallel  to 
the  edges  between  R  and  ooR  When  these  are  sharply  marked  the 
position  of  the  vertical  axis  is  easily  recognized  Many  crystals 
taper  sharply  toward  the  ends  of  the  c  axis  This  tapering  is  due  to 
oscillatory  combination  of  the  prism  ooR  with  rhombohedrons 

(Fig-  73)- 

The  habits  of  the  crystals  vary  with  the  crystallization  of  the  quartz. 
On  crystals  of  the  0  phase  the  +R  and  —  R  faces  are  equally  developed 
and  trigonal  trapezohedrons  are  absent.  The  crystals  are  hexagonal  in 



habit  Crystals  of  the  a  phase  usually  exhibit  marked  differences  in 
the  size  and  character  of  the  rhombohedral  planes,  and  trigonal  trape- 
zohedrons  may  be  present  on  them  Such  crystals  are  usually  trigonal 
in  habit  and  prismatic 

The  small  —(1121)  faces  on  all  types  of  crystals  (Fig   74)  are 


always  striated  parallel  to  the  edge  between  this  plane  and  +R.  By 
their  aid  the  +R  can  always  be  distinguished  from  the  —  R  This  is  a 
matter  of  some  practical  importance  since  plates  cut  from  quartz  crystals 
possess  the  power  of  rotating  a  ray  of  polarized  light.  The  plates  cut 

C  D 

FIG  75  —Supplementary  Twins  of  Quartz 

C  is  a  combination  of  A  and  B  in  Fig  74  twinned  about  *>  P2(ii2o)  This  is 
known  as  the  Brazil  law 

D  is  a  combination  of  two  crystals  like  B  twinned  about  c  as  the  twinning  axis 
One  is  revolved  60°  with  reference  to  the  others,  thus  causing  the  r  and  s  faces  to 
fall  together  Swiss  law  E  is  a  twin  like  D,  showing  portions  of  planes  belonging 
to  each  individual  It  contains  also  the  form  s. 

from  some  crystals  turn  the  ray  to  the  right;  those  cut  from  others  turn 
it  to  the  left  Crystals  that  produce  plates  of  the  first  kind  are  known 
as  right-handed  crystals,  those  that  produce  plates  of  the  second  kind  as 
left-handed  crystals.  Since  this  property  of  quartz  plates  is  employed 
in  the  construction  of  optical  instruments  for  use  m  the  detection  of 
sugars  and  certain  other  substances  in  solution  it  is  important  to  be 
able  to  distinguish  those  crystals  that  will  yield  right-handed  plates  from 
those  that  will  yield  left-handed  ones  Observation  has  shown  that 


when  the  -  (1121)  faces  are  in  the  upper  right-hand  corner  of  the  oo  R 

plane  immediately  beneath  +R  the  crystal  is  right-handed      When 
these  faces  are  in  the  upper  left-hand  corner  of  this  oo  R  plane  the  crystal 

OXIDES  163 

is  left-handed     In  either  case,  when       (5i5i)  is  present  it  occurs 


between  --  (1121)  and  the  oo  R  face  beneath  +R 

Interpenetration  t\\ms  of  quartz  are  so  common  that  few  crystals 
can  be  observed  that  do  not  exhibit  some  evidence  of  thinning  (Fig  75). 
The  twinning  plane  is  oo  R,  so  that  the  c  axes  in  the  twinned  individuals 
are  parallel  and,  indeed,  often  coincident  The  R  faces  and  the  oo  R 
faces  practically  coincide  in  the  twinned  parts  so  that  the  crystals 
resemble  untwinned  ones  The  twinning  is  exhibited  by  dull  areas  of 
—  R  on  bright  areas  of  +R  faces  and  by  breaks  in  the  continuity  of  the 
striations  on  oo  R 

Other  twinning  laws  have  also  been  observed  in  quartz,  but  their 
discussion  as  well  as  the  more  complete  discussion  of  the  mineral's 
crystallization  must  be  left  for  larger  treatises     In  the  most  common  of 
these  other  laws  the  individuals  are  thinned  about 
P2(ii22).     See  Fig   76 

The  fracture  of  quartz  is  conchoidal  Its  hard- 
ness is  7  and  density  2  65  Its  luster  is  \itreous,  or 
sometimes  greasy  Pure  specimens  are  transparent 
or  colorless,  but  most  varieties  are  colored  by  the 
addition  of  pigments  or  impurities  When  the 
coloring  matter  is  opaque  it  may  be  present  in 
sufficient  quantity  to  render  the  mineral  also  opaque  ^ 

on.        ±        i  IT-  *•  j     r  FlG      76—  Quart! 

The  streak  is  colorless  in  pure  varieties,  and  of  some     xwmned   about 
pale  shade  in  colored  varieties.    The  mineral  is  pyro-     p2(n22) 
electric  and  circularly  polarizing  as  described  above 
It  is  an  electric  insulator  at  ordinary  temperatures     Its  refractive 
indices  for  yellow  light  are:  o>=  i  5443,  €=  i  5534 

Quartz  resists  most  of  the  chemical  agents  except  the  alkalies.  It 
dissolves  in  fused  sodium  carbonate  and  in  solutions  of  the  caustic 
alkalies  It  is  also  soluble  in  HF  and  to  a  very  slight  degree  in  water, 
especially  in  water  containing  small  quantities  of  certain  salts  When 
heated  to  575°  the  a  variety  passes  into  the  /3  variety,  at  870°  both 
varieties  pass  into  tndymite,  and  at  1470°  the  tndymite  passes  over  into 
cristobahte.  Gradual  fusion  occurs  just  below  1470°. 

The  varieties  of  quartz  have  received  many  different  names  depend- 
ing largely  upon  their  color  and  the  uses  to  which  they  are  put.  They 
may  be  grouped  for  convenience  into  crystallized  and  crystalline  vari- 

The  principal  crystallized  varieties  are: 


Rock  crystal,  the  colorless,  transparent  variety,  that  often  forms 
distinct  crystals  This  is  the  variety  that  is  used  in  optical  instruments 
It  includes  the  Lake  George  diamonds,  rhmestones  and  Brazilian  peb- 

Amethyst,  the  violet-colored  transparent  variety. 

Rose  quartz,  the  rose-colored  transparent  variety. 

Citrine  or  false  topa~,  a  yellow  and  pellucid  kind 

Smoky  quartz  or  Cairngorm  stone,  a  smoky  yellow  or  smoky  brown 
variety  that  is  often  transparent  or  translucent,  but  sometimes  almost 

The  last  four  varieties  are  used  as  gems,  the  Cairngorm  stone  being  a 
popular  stone  for  mourning  jewelry 

M^lky  quartz  is  the  white,  translucent  or  opaque  variety  such  as  so 
commonly  forms  the  gangue  m  mineral  veins  and  the  material  of  "  quartz 

Sag&mte  is  rock  crystal  including  acicular  crystals  of  rutile 

Aventurine  is  rock  crystal  spangled  with  scales  of  some  micaceous 

The  puncipal  crystalline  varieties  are 

Chalcedony  ,  a  very  finely  fibrous,  transparent  or  translucent  waxy- 
looking  quartz  that  forms  mamillary  or  botryoidal  masses  Its  color  is 
white,  gray,  blue  or  some  other  delicate  shade  The  water  that  is  always 
present  in  it  is  believed  to  be  held  between  the  minute  fibers,  and  not  to 
be  combined  with  the  silica  (see  also  p  159) 

Carnehan  is  the  name  given  to  a  clear  red  or  brown  chalcedony 

Chrysoprase  is  an  apple-green  chalcedony 

Prase  is  a  dull  leek-green  variety  that  is  translucent 

Plasma  differs  from  prase  in  having  a  brighter  green  color  and  in 
being  translucent 

Heliotrope,  or  lloodstone,  is  a  plasma  dotted  with  red  spots  of  jasper. 

All  of  the  colored  chalcedonies  are  used  as  gems  or  as  ornamental 

Agate  is  a  chalcedony,  or  a  mixture  of  quartz  and  chalcedony  ,  vane- 
gated  in  color  The  commonest  agates  have  the  colors  arranged  in 
bands,  but  there  are  others,  like  "  fortification  agate  "  in  which  the 
colors  are  irregularly  distributed,  and  still  others  in  which  the  variation 
in  color  is  due  to  visible  inclusions,  as  in  "  moss-agates  "  The  different 
bands  in  banded  agates  often  differ  in  porosity.  This  property  is  taken 
advantage  of  to  intensify  the  contrast  in  their  colors  The  agate  is 
soaked  in  oil,  or  in  some  other  substance,  and  is  then  treated  with  chem- 
icals that  act  upon  the  material  absorbed  by  it  Those  bands  which 

OXIDES  165 

have  absorbed  the  greater  quantity  of  this  material  become  darker  in 
color  than  those  that  have  absorbed  less 

On)  %  is  a  very  evenly  banded  agate  in  which  there  is  a  marked  con- 
trast in  colors  Cameos  are  onyxes  in  one  band  of  which  figures  are  cut, 
leaving  another  band  to  form  a  background 

Sardonyx  is  an  onyx  in  which  some  of  the  bands  consist  of  carnelian. 
It  is  usually  red  and  white. 

Flint,  jasper,  hornstone  and  touchstone  are  very  fine  grained  crystalline 
aggregates  of  gray,  red  or  nearly  black  mixture  of  opal,  chalcedony  and 
quartz  They  are  more  properly  rocks  than  minerals  Chert  is  an  im- 
pure flint 

Sandstone  is  a  rock  composed  of  sand  grains,  most  of  tthich  are 
quartz,  cemented  by  clay,  calcite  or  some  other  substance.  When  the 
cement  is  quartz  the  rock  is  a  quartzite  Oilstones,  honestones  and  some 
whetstones  are  cryptocrystalhne  aggregates  of  quartz,  very  dense  and 
homogeneous,  except  for  tiny  rhombohedral  cavities  that  are  thought  to 
have  resulted  from  the  solution  of  crystals  of  calcite  They  are  gener- 
ally believed  to  be  beds  of  metamorphosed  chert 

Syntheses  — Crystallized  quartz  has  been  made  in  a  number  of  ways, 
both  from  superheated  aqueous  solutions  and  from  molten  magmas 
Crystals  have  been  produced  by  the  action  of  water  containing  am- 
monium fluoride  upon  powdered  glass  and  upon  amorphous  Si02,  and 
by  heating  water  in  a  dosed  glass  tube  to  high  temperatures  The 
separation  of  crystals  from  molten  magmas  is  facilitated  by  the  addition 
of  small  quantities  of  a  fluoride  or  of  tungsten  compounds. 

Occurrence  and  Origin  — Quartz  occurs  as  an  essential  constituent  of 
many  crystalline  rocks  such  as  granite,  gneiss,  etc.,  and  as  the  almost  sole 
component  of  certain  sandstones  It  constitutes  the  greater  portion  of 
most  sands  and  the  material  of  many  veins.  It  also  occurs  as  pseudo- 
morphs  after  shells  and  other  organic  bodies  embedded  in  rocks,  having 
replaced  the  original  substance  of  which  these  bodies  were  composed. 
It  is  also  one  of  the  decomposition  products  of  many  silicates.  It  may 
thus  be  primary  or  secondary  in  origin.  It  may  result  from  igneous  or 
aqueous  processes,  or  it  may  be  a  sublimation  product. 

Localities  — Quartz  is  so  widely  spread  in  its  distribution  that  only  a 
very  few  of  its  most  interesting  localities  can  be  referred  to  in  this  place. 

The  finest  specimens  of  rock  crystals  come  from  Dauphine,  France; 
Carrara,  in  Tuscany,  the  Piedmont  district,  in  Italy,  and  in  the  United 
States  from  Middleville,  and  Little  Falls,  N.  Y.;  the  Hot  Springs, 
Arkv  and  from  several  places  in  Alexander  Co.,  N.  C.  Smoky  quartz 
is  found  in  good  crystals  in  Scotland,  at  Pans,  Me.;  in  Alexander 


Co ,  N  C  ,  and  in  the  Pike's  Peak  region  of  Colorado  The  handsomest 
amethysts  come  from  Ceylon,  Persia,  Brazil,  Nova  Scotia  and  the 
country  around  Lake  Superior  Rose  quartz  occurs  in  large  quantity 
at  Hebron,  Pans,  Albany  and  Georgetown,  Me 

Fine  agates  and  carnehans  are  brought  from  Arabia,  India  and  Brazil. 
They  are  abundant  in  the  gravels  of  Agate  Bay  and  of  other  bays  and 
coves  on  the  north  shore  of  Lake  Superior 

Chalcedony  is  abundant  in  the  rocks  of  Iceland  and  the  Faroe  Islands, 
in  those  on  the  northwest  side  of  Lake  Supenor,  and  in  the  gravels  of 
the  Columbia,  the  Mississippi  and  other  western  rivers 

The  other  valuable  varieties  of  the  mineral  occur  largely  in  the  Far 

Agatized,  or  sihcified,  wood  of  great  beauty  exists  in  enormous  quan- 
tity in  an  old  petrified  forest  near  Cornzo,  Ariz  It  is  also  found  in 
the  Yellowstone  Park,  near  Florissant,  Colo  ,  and  in  other  places  in  the 
Far  West.  This  wood  has  had  all  of  its  organic  matter  replaced  mole- 
cule for  molecule  by  quartz  in  such  a  manner  that  its  original  structure 
has  been  perfectly  preserved 

Uses  — Rock  crystal  is  used  more  or  less  extensively  m  the  construc- 
tion of  optical  instruments  and  in  the  manufacture  of  cheap  jewelry 
Smoky  quartz,  amethyst,  onyx,  carnehan  and  heliotrope  stones  are 
used  as  gems,  and  agate,  prase,  chrysoprase  and  rose  quartz  as  orna- 
mental stones 

Milky  quartz,  ground  to  coarse  powder,  is  employed  in  the  manu- 
facture of  sandpaper.  Its  most  extensive  use,  however,  is  in  the  man- 
ufacture of  glass  and  pottery  Earthenware,  porcelain  and  some  other 
varieties  of  potter's  ware  are  vitrified  mixtures  of  clay  and  ground 
quartz,  technically  known  as  "flint "  Ordinary  glass  is  a  silicate  of 
calcium  or  lead  and  the  alkalies,  sodium  or  potash  It  is  made  by 
melting  together  soda,  potash,  lime  or  lead  oxide  and  ground  quartz  or 
quartz  sand,  and  coloring  with  some  metallic  salt  A  pure  quartz  glass 
is  now  being  made  for  chemical  uses  by  melting  pure  quartz  sand 

Quartz  is  sometimes  used  as  a  flux  in  smelting  operations  In  the 
form  of  sandstone,  it  is  used  as  a  building  stone,  and  in  the  form  of  sand 
it  is  employed  in  various  building  operations  Bncks  cut  from  dense 
quartzites  (very  hard  and  compact  sandstones)  are  often  employed 
for  lining  furnaces 

The  uses  of  honestones,  oilstones,  and  whetstones  are  indicated  by 
their  names. 

Production  — Many  varieties  of  quartz  are  produced  in  the  United 
Slates  to  serve  various  uses*  Vein  quartz  is  crushed  and  employed 

OXIDES  167 

in  the  manufacture  of  wood  filler,  paints,  pottery,  scouring  soaps,  sand- 
paper  and  abrasives  It  is  also  used  in  making  ferro-silicon,  chemical 
ware,  pottery,  sand-lime  brick,  quartz  glass,  etc  The  total  quantity 
produced  for  these  purposes  in  1912  was  97,874  tons,  valued  at 

The  largest  quantity  of  quartz  produced  is  in  the  form  of  sand,  of 
which  38,600,000  tons  were  marketed  in  1912  at  a  valuation  of  $15,300,- 
ooo  Sandstone,  valued  at  $6,900,000,  was  quamed  for  building  and 
paving  purposes  Oilstones,  grindstones,  millstones,  etc.,  which  are 
made  from  special  varieties  of  sandstone,  were  produced  to  the  value  of 

Gem  quartz  obtained  in  1912  was  valued  at  about  $22,000.  This 
comprised  petrified  wood,  chrysoprase,  agate,  amethyst,  rock  crystal, 
smoky  quartz,  rose  quartz,  and  gold  quartz  (white  quartz  containing 
particles  of  gold). 


The  metallic  dioxides  include  the  oxides  of  tin,  titanium,  manganese 
and  lead  Of  these  the  manganese  dioxide  may  be  dimorphous,  and  the 
titanium  dioxide  is-tnmorphous.  A  dioxide  of  zirconium  is  also*  known, 
baddeleytfe,  but  it  is  extremely  rare.  The  mineral  zircon  (ZrSiO4)  is 
often  regarded  as  being  isomorphous  with  cassttente  (Sn02)  and  rutile 
(Ti02)  because  of  the  similarity  in  the  crystallization  of  the  three  min- 
erals The  three,  therefore,  are  placed  in  the  same  group,  in  which 
case  all  must  be  regarded  as  salts  of  metallic  acids,  thus:  Ti02=TiTiO4, 
SnO2=SnSn04,  zircon =ZrSi04  Other  authorities  regard  zircon  as  an 
isomorphous  mixture  of  Ti02  and  Si02.  In  this  book  zircon  is  placed 
with  the  silicates  and  the  other  minerals  are  considered  as  oxides. 

The  two  manganese  dioxides  are  poliantfe  and  pyrolusite.  The  former 
is  tetragonal  and  the  latter  orthorhombic  It  is  possible,  however,  that 
the  crystals  of  pyrolusite  are  pseudomorphs  and  that  the  substance  is  a 
mixture  of  poliamte  and  some  hydroxide,  as  it  nearly  always  contains 
about  2  per  cent  HgO. 

The  three  titanium  oxides  are  ridde,  which  is  tetragonal;  brookitc, 
which  is  orthorhombic,  and  anatase  or  octakednte,  which  is  tetragonal. 
Although  rutile  and  anatase  crystallize  in  the  same  system,  their  axial 
ratios  are  different,  as  are  also  their  crystal  habits  and  their  physical 
properties.  A  few  of  these  differences  are  indicated  below: 

Rutde    a:c=i:    .6439;   Sp.  Gr.  =4-283;  «»=  2.6158;  $«=  2.9029. 
Anatase         -1:1.7771;   Sp.  Gr.  =3.9    ;  ^=2.5618;  ^=2.4886. 


Of  the  tliree  modifications  of  titanium  dioxide,  anatase  may  be 
made  at  a  comparatively  low  temperature  Brookite  requires  a  higher 
temperature  for  its  production,  but  rutilfc  is  producible  at  both  high 
and  low  temperatures  Under  the  conditions  of  nature  both  brookite 
and  anatase  pass  readily  into  rutile 

Of  the  seven  dioxides  discussed,  four  are  members  of  a  single  group 


The  rutile  group  consists  of  four  minerals  apparently  completely 
isomorphous,  though  no  mixed  crystals  of  any  two  have  been  discovered  : 
All  crystallize  in  the  tetragonal  system  (ditetragonal  bipyramidal  class), 
with  the  same  forms  and  with  closely  corresponding  axial  ratios  The 
names  of  the  members  of  the  group  and  their  axial  ratios  follow 

Cassitente (Sn02)  a  •  c  =i  .  6726 

Ruttle        (Ti02)  =i  •  6439 

Pohamte   (Mn02)  =i  '  6647 

Plattnente (PbOa)  =i  '  6764 

Cassiterite  (Sn02) 

Cassiterite,  or  tinstone,  is  the  only  worked  ore  of  tin  It  occurs  as 
rolled  pebbles  of  a  dark  brown  color  in  the  beds  of  streams,  as  fibrous 
aggregates,  and  as  ghstemng  black  crystals  associated  with  other  min- 
erals in  veins 

The  analyses  of  cassitente  indicate  it  to  be  essentially  an  oxide  of 
tin,  or,  possibly,  a  stanyl  stannale  ((SnOJSnOa),  with  the  composition, 
Sn=78.6  per  cent;  0=2i  4  per  cent.  The  mineral  nearly  always  con- 
tains some  iron  oxide  and  often  oxides  of  tantalum,  of  zinc  or  of  arsenic 
The  presence  of  iron  and  tantalum  is  so  general  that  most  crystals  of 
cassitente  may  be  regarded  as  isomorphous  mixtures  of  (SnO)(SnOs); 
Fe(SnOs)  and  Fe(TaOs)2-  Thus,  a  crystal  from  the  Etta  Mine  in  the 
Black  Hills,  S.  D,  gave  Sn02=9436;  FeO-i62,  Ta205=242  and 
8102=100,  indicating  a  mixture  of  5  pts  of  Fe(TaOs)2,  18  pts.  of 
Fe(SnOs)  and  303  5  pts  of  (SnO)(SnOs). 

The  crystals  of  cassitente  have  an  axial  ratio  of  i :  ,6726.  They  are 
usually  short  prisms  in  habit  They  often  consist  of  the  simple  com- 
bination P(in)  and  POO(IOI)  (Fig  77),  or  of  these  forms,  together 
with  sPf  (321)  and  various  prisms  (Fig  78).  Twins  are  common,  the 

1An  isomorphous  mixture  of  the  rutile  and  cassitente  molecules  has  recently 
been  described  from  Greifenstem,  Austria,  but  its  existence  has  not  yet  been  con- 



twinning  plane  being  P  oo  (101)  When  the  individuals  twinned  have 
small  prismatic  faces  the  resulting  combination  is  often  called  a  visor 
twin  (Fig  79),  because  of  its  supposed  resemblance  to  the  vitor  of  a 
helmet  By  repetition  of  the  twinning  very  complex  groupings  are 
produced  The  angle  in  A  * ^*  —  58°  19' 

FIG  77  FIG  78 

FIG.  77. — Cassitente  Crystal  with  P,  m  (s)  and  P  * ,  101  fc) 
FIG  78.— Cassitente  Crystal  with  s,  e  and  °o  P,  no  (m),  «o P2,  210  (A),  3pJ,  321  (=). 

The  cleavage  of  cassitente  is  imperfect  parallel  to  oo  P  oo  (100)  and 
P(III)  Its  fracture  is  uneven  The  color  of  the  massive  mineral  is 
some  dark  shade  of  brown  by  reflected  light,  and  of  the  crystals  black 
By  transmitted  light,  the  mineral  is  brown  or  black  Its  luster  is  very 
brilliant,  and  its  streak  is  white,  gray  or  brown.  The  purest  specimens 

FIG  79 —Cassitente Twinned  about  P «5 (101),   o=ooPoo,ioo    A=*VisorTwin. 

are  nearly  transparent,  though  the  ordinary  varieties  are  opaque  Their 
hardness  is  about  6  5  and  density  about  7  The  mineral  is  a  noncon- 
ductor of  electricity  Its  refractive  indices  for  yellow  light  are:  w  =  1 9965, 

Three  varieties  of  cassitente  are  recognized,  distinguished  by  physical 
characteristics     The  ordinary  variety  known  as  tinskme  is  crystallised 


or  massive.  Wood  tin  is  a  botryoidal  or  remform  variety,  concentric  in 
structure  and  composed  of  radiating  fibers  The  third  variety  is  stream 
tin  This  consists  of  water-worn  pebbles  found  m  the  beds  of  streams 
that  flow  over  cassitente-bearmg  rocks 

Cassitente  is  only  slightly  acted  upon  by  acids  It  may  be  reduced 
to  a  metallic  globule  of  tin  only  with  difficulty,  even  when  mixed 
with  sodium  carbonate  and  heated  intensely  on  charcoal.  With 
borax  it  yields  slight  reactions  for  iron,  manganese  or  other  impurities 
When  placed  in  dilute  hydrochloric  acid  with  pieces  of  granulated  zinc, 
fragments  of  cassiterite  become  covered  with  a  dull  gray  coating  of 
metallic  tin  which  can  be  burnished  by  rubbing  with  a  doth  or  the  hand 
When  rubbed  by  the  hand  the  odor  of  tin  in  contact  with  flesh  is  easily 

The  mineral  is  most  easily  distinguished  from  other  compounds  that 
resemble  it  in  appearance  by  its  high  density  and  its  inertness  when 
treated  with  reagents  or  before  the  blowpipe 

Syntheses  —Crystals  of  cassiterite  have  been  obtained  by  passing 
steam  and  vapor  of  tin  chloride  or  tin  fluoride  through  red-hot  porcelain 
tubes,  and  by  the  action  of  tin  chloride  \apor  upon  lime 

Occurrence  and  Origin. — Tinstone  is  found  as  a  primary  mineral  in 
coarse  granite  veins  with  topaz,  tourmaline,  fluorite,  apatite  and  a  great 
number  of  other  minerals  It  also  occurs  impregnating  rocks,  sometimes 
replacing  the  minerals  of  which  they  originally  consisted.  In  these 
cases  it  is  the  product  of  pneumatolytic  processes.  In  many  places  it 
constitutes  a  large  proportion  of  the  gravel  in  the  beds  of  streams 

Localities  and  Production  — The  crystallized  mineral  occurs  at  many 
places  in  Bohemia  and  in  Saxony,  at  Limoges  in  France  and  sparingly 
in  a  few  places  in  the  United  States,  especially  near  El  Paso,  Texas, 
in  Cherokee  Co.,  N.  C  ,  in  Lincoln  Co ,  S  C  ,  and  near  Hill  City,  S  D 
Massive  tinstone  and  stream  tin  occur  in  laige  enough  quantities  to  be 
mined  in  Cornwall,  England,  on  the  Malay  Peninsula  and  on  the  islands 
lying  off  its  extremity;  in  Tasmania;  in  New  South  Wales,  Victoria 
and  Queensland,  Australia;  in  the  gold  regions  of  Bolivia,  at  Durango 
in  Mexico,  and  at  various  points  in  Alaska,  at  some  of  which  there, 
are  400  Ib.  of  cassiterite  in  a  cubic  yard  of  gravel. 

The  principal  tin  ore-producing  regions  of  the  world  are  the  Straits, 
district,  including  the  Malay  Peninsula  and  the  islands  of  the  Malay 
Archipelago;  Australia;  Cornwall,  England,  the  Dutch  East  Indies,  and 
Bolivia*  Of  the  total  output  of  122,752  tons  of  tin  produced  m  1911, 
61,712  tons  were  made  from  the  Straits  ore,  25,312  tons  from  the  ore 
produced  in  Bolivia  and  16,800  tons  from  Banka  ore.  Of  the  total 



quantity  of  tin  produced  about  78  per  cent  is  said  to  come  from  stream 
tin  and  22  per  cent  from  ore  obtained  from  veins.    The  quantity 
obtained  from  ore  mined  in  the  United  States  in  igu  included  61  tons 
from  Alaskan  stream  tin  and  two  tons  from  the  tinstone  mined  in  the 
Franklin  Mountains  near  El  Paso,  Texas     Mines  have  been  opened  in 
San  Bernardino  Co  ,  California,  and  in  the  Black  Hills,  South  Dakota, 
but  they  have  not  proved  successful     The  mines  at  El  Paso,  Texas,  are 
not  yet  fully  developed,  although  they  promise  to  be  profitable  in  the 
near  future     The  crystals  are  scattered  through  quartz  veins  and 
through  a  pink  granite  near  the  contacts  with  the  veins     The  average 
composition  of  the  ore  is  2  per  cent     This  is  concentrated  to  a  60  per 
cent  ore  before  being  smelted     The  production  during  1912  was  130 
tons  of  stream  tin  from  Buck  Creek,  Alaska     This  was  valued  at 
$124,800.    In  the  following  year  3  tons  of  cassitente  ^ere  shipped  from 
Gaffney,  S  C     The  imports  of  tin  into  the  United  States  during  1911 
were  53,527  tons  valued  at  more  than  $43,300,000 

Enaction  — The  tin  is  extracted  from  the  concentrated  ore  by  the 
simple  process  of  reduction  Alternate  layers  of  the  ore  and  charcoal 
are  heated  together  in  a  furnace,  when  the  metal  results  This  collects 
in  the  bottom  of  the  furnace  and  is  ladled  or  run  out  The  crude  metal  is 
refined  by  remeltmg  m  special  refining  furnaces 

Uses  of  the  Metal  — The  metal  tin  is  employed  principally  for  coating 
other  metals,  either  to  prevent  rusting  or  to  pre\ent  the  action  upon 
them  of  chemical  reagents  Tin  plate  is  thin  sheet  iron  covered  with 
tin  Copper  for  culinary  purposes  is  also  often  co\  ered  with  this  metal 
It  is  used  also  extensively  in  forming  alloys  with  copper,  antimony, 
bismuth  and  lead  Among  the  most  important  of  these  alloys  are 
bronze,  bell  metal,  babbitt  metal,  gun  metal,  britanma,  pewter  and  soft 
solder  Its  alloy,  or  amalgam,  with  mercury  is  used  in  coating  mirrors. 
Several  of  its  compounds  also  find  uses  m  the  arts  Tin  oside  is  an  im- 
portant constituent  of  certain  enamels  The  chlorides  are  used  exten- 
sively in  dyeing  calicoes,  and  the  bisulphide  constitutes  "  bronze 
powder  "  or  "  mosaic  gold,"  a  powder  employed  for  bronzing  plaster, 
wood  and  metals 

Rutile  (Ti02) 

Rutile  is  one  of  the  oxides  of  the  comparatively  rare  element  titanium. 
It  occurs  commonly  m  dark  brown  opaque  cleavable  masses  and  in  bril- 
liant black  crystals 

Pure  rutile  consists  of  40  per  cent  0  and  60  per  cent  TL  Nearly  all 
specimens,  however,  contain  in  addition  some  iron,  occasionally  as  much 



as  9  per  cent  or  10  per  cent,  which  is  probably  due  to  the  admixture  of 

and  FeTiOs  in  solid  solution 

Rutile  is  perfectly  isomorphous  with  cassiterite  Its  axial  ratio  is 
i  :  6439  The  pnncipal  planes  observed  on  its  crystals  are  practically 
the  same  as  those  observed  on  cassiterite  (Fig  80)  Twins  aie  common, 
with  P  oo  (101)  the  twinning  plane  (Fig  81 )  This  twinning  is  often 
repeated,  producing  elbow-shaped  groups  (Fig  82),  or  by  further  repe- 

FIG  So.— Rutile  Crystals  with  «o  P,  no  (m),  oo  p  oo  ,  100  (a),  P  oo  ,  yoi  (e),  P,  111(5), 
«>P3>  3io  (0,  p3»  313  (0  and  3PJ,  321  00 

FIG  81 

FIG  82 

FIG  81  —Rutile  Eightling  Twinned  about  P  oo  (101) 
FIG  82  —Rutile  Twinned  about  P  oo  (101)     Elbow  Twin 

tition  wheel-shaped  aggregates  (Fig  83)  In  another  common  law  the 
twinning  plane  is  3?  oo  (301")  (Fig  84)  The  angle  in  A  iTx  —  56°  52^' 
The  crystals  are  prismatic  and  even  sometimes  acicular  in  habit.  Their 
prismatic  planes  are  vertically  striated 

The  cleavage  of  rutile  is  quite  distinct  parallel  to  oo  P(no)  and  less 
so  parallel  to  oo  P  oo  (100) 

The  mineral  is  reddish  brown,  yellowish  brown,  black  or  bluish 
brown  by  leflected  light  and  sometimes  deep  red  by  transmitted  light, 
Many  specimens  are  opaque  but  some  are  translucent  to  transparent. 



The  latter  are  often  pleochroic  in  tints  varying  between  yellow  and 
blood-red  The  streak  is  pale  brown  The  hardness  of  the  mineral  is 
6  to  6  5  and  its  density  about  42  It  is  an  electric  nonconductor  at 
ordinary  temperatures  Its  refractive  indices  for  yellow  light  are: 
o>=  2  6030,  €=2  8894. 

Rutile  is  infusible  and  insoluble.  Its  reactions  with  beads  of  borax 
and  microcosmic  salt  are  usually  obscured  by  the  iron  present  When 
this  metal  is  present  only  in  small  quantities  the  microcosmic  salt  bead 
is  colorless  while  hot,  but  violet  when  cold,  if  it  has  been  heated  for  some 
time  in  the  reducing  flame  of  the  blowpipe 

The  most  characteristic  chemical  reaction  of  rutile  is  obtained  upon 
fusing  it  with  sodium  carbonate  on  charcoal,  dissolving  the  fused  mass  in 

FIG  83.  FIG  84 

FIG  83  —Rutile  Cyclic  Sixling  Twinned  about  P  « (101) 

FIG  84  — Rutile  Twinned  about  3?  » (301)     Elbow  Twin     Forms    °°  P2,  210  (A), 

and  P  °o ,  ioi  (e) 

an  excess  of  hydrochloric  acid  and  adding  to  the  solution  small  scraps  of 
tin  Upon  heating  for  some  little  time,  the  solution  assumes  a  violet 
color.  This  is  a  universal  test  for  the  metal  titanium 

Some  of  the  dark  red  and  reddish  brown  massive  varieties  of  rutile 
may  be  confounded  with  some  varieties  of  garnet,  which,  however,  are 
much  harder.  Its  density,  its  infusibihty  and  the  reaction  for  titanium 
serve  to  characterize  the  mineral  perfectly 

Pseudomorphs  of  rutile  after  hematite  and  after  brookite  and  ana- 
tase  have  been  described  It  often  changes  into  ilmenite  and  sphene. 

Syntheses. — By  the  reaction  between  TiCU  and  water  vapcr  in  a  red- 
hot  porcelain  tube,  crystals  of  rutile  are  formed.  Twins  are  produced 
by  submitting  precipitated  titanic  acid  in  a  mass  of  molten  sodium  tung- 
state  to  a  temperature  of  1000°  for  several  weeks. 

Occurrence  and  Origin  —Rutile  is  often  found  as  crystals  embedded 
in  limestone  and  m  the  quartz  or  f  eldspar  of  granite  and  other  igneous 


rocks,  as  long  acicular  crystals  m  slates,  and  as  grams  in  the  rock  known 
as  nelsomte  It  occurs  also  as  fine  hair-like  needles  penetrating  quartz, 
forming  the  ornamental  stone  "  fleches  d'amour,"  and  as  grains  in  the 
gold-bearing  sand  regions  When  primary  it  is  probably  always  a 
product  of  magmatic  processes,  either  crystallizing  from  a  molten  magma 
or  being  the  result  of  pneumatolysis. 

Localities  — Handsome  crystals  of  the  mineral  occur  at  Arendal,  in 
Norway,  in  Tyrol,  and  at  St  Gothard  and  in  the  Binnenthal,  Switzer- 
land In  the  United  States  large  crystals  have  been  obtained  at  Barre, 
Mass  ,  at  Sudbury,  Chester  Co ,  Penn  ;  at  Stony  Point,  Alexander  Co  , 
N  C  ,  at  Graves  Mt ,  in  Georgia,  at  Magnet  Cove,  in  Arkansas,  and 
in  Nelson  Co ,  Va.  In  the  latter  place  it  occurs  in  large  quantity  as 
crystals  disseminated  through  a  coarse  granite  rock  The  rock  con- 
taining about  10  per  cent  of  rutile  is  mined  as  an  ore  It  constitutes  the 
principal  source  of  the  mineral  in  the  United  States  A  second  type 
of  occurrence  in  the  same  locality  is  a  dike-like  rock,  nelsomte,  composed 
of  ilmemte  and  apatite,  in  which  the  ilmemte  is  in  places  almost 
completely  replaced  by  rutile 

Uses  — The  mineral  is  not  of  great  economic  importance  It  is  used 
in  small  quantity  to  impart  a  yellow  color  to  porcelain  and  to  give  an 
ivory  tint  to  artificial  teeth.  It  is  also  used  in  the  manufacture  of  the 
alloy  ferro-titamum  which  is  added  to  steel  to  increase  its  strength 
Recently  the  use  of  titamferous  electrodes  in  arc  lights,  and  the  use  of 
titanium  for  filaments  in  incandescent  lamps  ha\e  been  proposed  Some 
of  the  salts  of  titanium  are  used  as  dyes  and  others  as  mordants  Most 
of  the  ferro-titamum  made  m  the  United  States  is  manufactured  from 
titamferous  magnetite 

Production  — The  only  rutile  mined  in  the  United  States  during  1913 
came  from  Roseland,  Nelson  Co.,  Virginia.  It  amounted  to  305  tons  of 
concentrates  containing  about  82  per  cent  TiOs  At  the  same  time  there 
were  separated  about  250  tons  of  ilmemte  (see  p  462) 

Polianite  (MnC^I  is  usually  in  groups  of  tiny  parallel  crystals  and 
as  crusts  of  crystals  enveloping  crystals  of  manganite  (MnO  OH).  Their 
axial  ratio  is  i  '  6647  The  color  of  the  mineral  is  iron-gray.  Its  streak 
is  black,  its  hardness  6-6  5  and  density  4  99.  It  dissolves  in  HC1  evolv- 
ing chlorine  It  is  distinguished  from  pyrolusite  by  its  greater  hardness 
and  its  lack  of  water  The  mineral  is  extremely  rare,  being  found  in 
measurable  crystals  only  at  Platten  in  Bohemia  It  occurs  in  pseudo- 
morphs  after  manganite  at  a  number  of  other  points  m  Europe  and  at  a 
few  points  elsewhere,  but  in  most  cases  it  has  not  been  dearly  distin- 

OXIDES  175 

guished  from  pyrolusite  The  rarity  of  its  crystals  is  regarded  by  some 
mineralogists  as  being  due  to  the  fact  that  in  most  of  its  occurrences 
poliamte  is  colloidal  (a  gel) 

Plattnerite  (PbO2)  is  usually  massive,  but  it  occurs  in  prismatic 
crystals  near  Mullan  in  Idaho  Their  axial  ratio  is  i  :  6764  They  are 
usually  bounded  by  oo  P  oo  (100),  3?  oo  (301),  P  oo  (101),  oP  (ooi)  and 
often  IP  (33 2)  The  mineral  is  found  also  in  crusts  Its  color  is 
iron-black  and  its  streak  chestnut-brown  Its  hardness  is  5-5  5  and 
its  density  86  It  is  brittle  and  is  easily  fusible  before  the  blow- 
pipe, giving  off  oxygen  and  coloring  the  flame  blue  It  yields  a  lead 
bead  It  is  difficultly  soluble  in  HNOs,  but  easily  soluble  in  HC1  with 
evolution  of  chlorine.  Plattnente  is  found  at  Leadhills  and  at  Wanlock- 
head,  Scotland,  and  at  the  "  As  You  Like  "  Mine  near  Mullan,  Idaho. 


Pyrolusite  is  often  the  result  of  the  alteration  of  the  hydroxide,  man- 
gamte,  or  of  pohamte.  The  few  measurable  crystals  that  have  been 
studied  seem  to  indicate  that  their  form  is  pseudomorphic  after  the 
hydroxide  The  change  by  which  manganite  may  pass  over  into  pyro- 
lusite is  represented  by  the  reaction  2MnO(OH)-f-0=2Mn02+H2O. 
Pyroiusite  may  be,  however,  only  a  slightly  hydrated  form  of  poliamte. 

An  analysis  of  a  specimen  from  Negaunee,  Mich.,  gave 

MnO         O         CaO     BaO    SiOa         Limomte         HgO  Total 

79  46      17  48        18        38        18  .31  i  94  99  93 

Pyrolusite,  as  usually  found,  is  in  granular  or  columnar  masses,  or  in 
masses  of  radiating  fibers  It  is  a  soft,  black  mineral  with  a  hardness  of 
only  2  or  2  5  and  a  density  of  about  4.8  Its  luster  is  metallic  and  its 
streak  black  It  is  a  fairly  good  conductor  of  electricity. 

The  reactions  of  this  mineral  are  practically  the  same  as  those  of 
pohanite  and  manganite  (see  p  191),  except  that  only  a  small  quantity 
of  water  is  obtained  from  it  by  heating.  Upon  strong  heating  it  yields 
oxygen,  according  to  the  equation  3Mn02=Mn3+3Q2- 

The  manganese  minerals  are  easily  distinguished  from  other  minerals 
by  the  violet  color  they  give  to  the  borax  bead  and  by  the  green  prxjduct 
obtained  when  they  are  fused  with  sodium  carbonate.  Pyrolusite  is 
distinguished  from  manganite  by  its  physical  properties,  and  from 
amte  by  its  softness 


Localities  —  -Pyrolusite  is  worked  at  Elgersberg,  near  Ilmenau  in 
Thuringia,  at  Vorder  Ehrensdorf  in  Moravia,  at  Flatten  in  Bohemia, 
at  CartersviUe,  Ga  ,  at  Batesville,  Ark  ,  and  m  the  Valley  of  Virginia 
A  manganiferous  silver  ore  containing  considerable  quantities  of  pyro- 
lusite  is  mined  in  the  Leadville  district,  Colorado,  and  large  quan- 
tities of  manganiferous  iron  ores  are  obtained  in  the  Lake  Superior 

Uses  —  Pyrolusite,  together  with  the  other  manganese  ores  with 
which  it  is  mixed,  is  the  source  of  nearly  all  the  manganese  compounds 
employed  in  the  arts  Some  of  the  ores,  moreover,  are  argentiferous 
and  others  contain  zinc  From  these  silver  and  zinc  are  extracted  The 
most  important  use  of  the  mineral  is  in  the  iron  industry.  In  this  indus- 
try, however,  much  of  the  manganese  employed  is  obtained  from  man- 
gamferous  iron  ores  The  alloys  spiegeleisen  and  ferro-manganese  are 
employed  very  largely  in  the  production  of  an  iron  used  m  casting  car 
wheels.  It  is  extremely  hard  and  tough  The  manganese  minerals  are 
also  used  in  glass  factories  to  neutralize  the  green  color  imparted  to  glass 
by  the  ferruginous  impurities  m  the  sands  from  which  the  glass  is  made 
They  are  also  used  m  giving  black,  brown  and  violet  colors  to  pottery 
and  some  of  their  salts  are  valuable  mordants  Pyrolusite,  finally,  is  the 
principal  compound  by  the  aid  of  which  chlorine  and  oxygen  are  pro- 

Production  —  The  United  States  in  1912  produced  about  1,664  tons 
of  manganese  ores,  valued  at  $15,723,  and  all  came  from  Virginia,  South 
Carolina  and  California  In  previous  years  the  ores  had  been  mined 
also  m  Arkansas,  Tennessee  and  Utah  Moreover,  there  were  imported 
into  the  country  300,661  tons,  valued  at  $1,769,000  Nearly  all  of  this 
was  used  in  the  manufacture  of  spiegeleisen  The  domestic  product  was 
used  in  the  chemical  industries  largely  in  the  manufacture  of  manganese 
brick  Of  the  manganiferous  iron  ores  about  818,000  tons  were  produced 
ui  1912  These  were  utilized  mainly  as  ores  of  iron,  though  a  large  por- 
tion was  used  as  a  flux.  The  product  of  manganiferous  silver  ores  aggre- 
gated about  48,600  tons,  all  of  which  was  used  as  a  flux  for  silver-lead 
ores.  Nearly  all  of  this  came  from  Colorado  In  addition  there  were 
imported  iron-manganese  alloys  valued  at  $3,935,000. 

Anatase  and  BrooMte 

As  has  already  been  stated,  the  compound  Ti02  is  trimorphous,  one 
form  being  orthorhombic  and  the  two  others  tetragonal  Of  the  latter, 
one  has  already  been  described  as  rutile  The  other  is  anatase,  or  octa- 
hednte.  The  orthorhombic  form  is  known  as  brookite  Anatase  and 

OXIDES  177 

rutile  are  separated  because  of  the  difference  in  their  axial  ratios  and  in 
the  habits  of  their  crystals  Both  are  ditetragonal  bipyramidal,  but 
a :  c  for  rutile  is  i  :  6439  and  for  anatase  i  .  i  7771  Brookite  is 
orthorhombic  bipyramidal  with  a :  b  •  c-  8416  :  i  :  .9444. 

Both  anatase  and  brookite  have  the  same  empirical  composition, 
which  is  similar  to  that  of  rutile 

Crystals  of  anatase  are  usually  sharp  pyramidal  with  the  form  P(in) 
predominating  (Fig  85),  blunt  pyramidal  with  |P(ii3)  or  $P(ii7) 
predominating  (Fig  86),  or  tabular  parallel  to  oP(ooi)  Twins  are 
common  in  some  localities,  with  P  oo  (101)  the  twinning  plane.  The 
angle  in  A  iTiaBS82°  91' 

The  mineral  is  colorless  and  transparent,  or  dark  blue,  yellow,  brown 

FIG  86 

FIG  85  — Anatase  Crystal  with  P  in  (p) 

FIG  86— Anatase  Crystal  with  fP,  113  (s),  P,  in  (p),  IP,  117  fr);    °°P»  «o  (*»), 
oo  P  oo ,  100  (a)  and  P  GO  ,  101  (t) 

or  nearly  black  and  almost  opaque  Its  streak  is  colorless  to  light 
yellow.  Its  cleavage  is  perfect  parallel  to  P  and  oP  and  its  fracture 
conchoidal  Its  hardness  is  between  5  and  6  and  its  density  is  3.9.  This 
increases  to  4  25  upon  heating  to  a  red  heat,  possibly  due  to  its  partial 
transformation  into  rutile  The  mineral  is  insoluble  in  acids  except 
hot  concentrated  EkSO-i.  It  is  a  nonconductor  of  electricity.  Its 
indices  of  refraction  for  yellow  light  are  w=  2  5618,  e=  2  4886 

Brooktte  crystals  are  usually  tabular  parallel  to  oo  P  60  (too)  and 
elongated  in  the  direction  of  the  c  axis  Nearly  all  crystals  are 
striated  in  the  vertical  zone  Although  many  forms  have  been  identi- 
fied on  them,  by  far  the  most  common  is  P2(i22)  In  some  cases  this  is 
the  only  pyramidal  form  present,  as  in  the  type  known  as  arkanstie 
(Fig.  87)  Twins  are  rare,  with  oo  ¥2(210)  the  twinning  plane.  The 
angle  in  AiTi==:640  17'. 



Brookite  may  be  opaque,  translucent  or  transparent  Its  color 
vanes  from  yellowish  brown,  through  brownish  red,  to  black  (arkansite) 
Its  streak  is  brownish  yellow  Its  clea\age  is  imperfect  parallel  to 
oo Poo  (101),  and  its  fracture  uneven  or  conchoidal  Its  hardness  is 
5-6  and  density  about  4,  Upon  heating  its  density  increases  to  that  of 
rutile  Its  refractive  indices  for  yellow  light  are  a= 2  5832,  #=  2  5856, 
7=2  7414  It  fuses  at  about  1560°,  and  is  insoluble  in  acids 

The  chemical  properties  of  both  brookite  and  anatase  are  similar 
to  those  of  rutile  They  are  distinguished  from  rutile  by  their  physical 
properties  and  their  crystallization 

Both  brookite  and  anatase  alter  to  rutile 

Syntheses  —Upon  heating  TiFi  with  water  vapor  at  a  temperature 

FIG  §7— Brookite  Crystals  with  coP,  no  (w),   JP,  112  (z)  and  PsT,  122  (e) 
combination  m  and  e  is  characteristic  for  \rkanbitc 


below  that  of  vaporizing  cadmium,  crystals  of  anatase  are  produced. 
If  the  temperature  is  raised  above  the  point  of  vaporization  of  cadmium 
and  kept  below  that  of  zinc,  crystals  of  brookite  result 

Occurrence  — Brookite  and  anatase  occur  as  crystals  on  the  walls  of 
clefts  in  crystalline  silicate  rocks  and  in  weathered  phases  of  volcanic 
rocks.  They  are  mainly  pneumatolytic  products,  the  production  of  the 
one  or  the  other  depending  upon  the  temperature  at  which  the  TiCfe  was 

Localities — Fine  brookite  crystals  are  found  at  St  Gothard,  in 
Switzerland,  at  Pregrattan,  in  the  Tyrol,  near  Tremadoc,  in  Wales, 
at  Miask,  in  Russia,  and  at  Magnet  Cove,  Arkansas 

Anatase  crystals  are  less  common  than  those  of  brookite  but  they 
occur  at  many  points  in  Switzerland,  especially  in  the  Binnenthal, 
near  Bourg  d'Oisans,  France,  at  many  points  in  the  Urals,  Russia,  in 
the  diamond  fields  of  Brazil,  and  at  the  brookite  occurrences  m  Arkansas, 




THE  hydroxides,  as  has  already  been  explained,  may  be  looked  upon 
as  derivatives  of  water,  m  which  only  a  portion  of  the  hydrogen  has  been 
replaced.  The  group  includes  several  minerals  of  economic  importance, 
among  which  is  the  fine  gem  mineral  opal  All  the  hydroxides  yield 
water  when  heated  in  a  glass  tube,  but  they  do  not  yield  it  as  readily  as 
do  salts  containing  water  of  crystallization 

A  few  of  the  hydroxides  may  act  as  acids  forming  salts  with  metals 
Diaspore,  for  instance,  is  an  hydroxide  of  aluminium  A10-OH,  or 


Al<          ,  which  appears  to  be  able  to  form  salts,  at  least,  the  chemical 

composition  of  some  of  the  members  of  an  important  group  of  minerals, 
the  spinels,  may  be  explained  by  regarding  them  as  salts  of  this  acid 
(seep  195) 

Opal  (Si02+Aq) 

The  true  position  of  opal  in  the  classification  of  minerals  is  somewhat 
doubtful  From  the  analyses  made  it  appears  to  be  a  combination  of 
amorphous  silica  and  water,  or,  perhaps,  a  mixture  of  silica  in  some  form 
and  a  hydroxide  of  silicon  The  percentage  of  water  present  is  variable. 
In  some  specimens  it  is  as  low  as  3  per  cent,  while  in  others  it  is  as  high 
as  13  per  cent  The  mineral  is  not  known  in  crystals.  It  is  probably  a 
colloid,  in  which  the  water  is,  in  part  at  least,  mechanically  held  in  a  gel 
of  SiCfe.  It  occurs  only  m  massive  form,  in  stalactitic  or  globular  masses 
and  in  an  earthy  condition. 

When  pure  the  mineral  is  colorless  and  transparent  Usually,  how- 
ever, it  is  colored  some  shade  of  yellow,  red,  green  or  blue,  when  it  is 
translucent  or  sometimes  even  opaque.  The  red  and  yellow  varieties  con- 
tain iron  oxides  and  the  green,  prasopd,  some  nickd  compound  The 
play  of  color  in  gem  opal  is  due  to  the  interference  of  light  rays  reflected 
from  the  sides  of  thin  layers  of  opal  material  with  different  densities 
from  that  of  the  mam  mass  of  the  mineral  they  traverse.  The  hardness 
of  opal  is  5  5-6  $  and  its  density  about  2.1  Its  refractive  index  for 
yellow  light,  n= 1.4401,  It  is  a  nonconductor  of  electricity. 



The  principal  varieties  of  opal  are 

Precwus  opal,  a  transparent  variety  exhibiting  a  delicate  play  of 

Fire  opal,  a  precious  opal  in  which  the  colors  are  quite  brilliant 
shades  of  red  and  yellow, 

Girasol,  a  bluish  white  translucent  opal  with  reddish  reflections, 

Common  opal,  a  translucent  variety  without  any  distinct  play  of 

Cachalong,  an  opaque  bluish  white,  porcelain-like  variety, 

Hyalite,  a  transparent,  colorless  variety,  usually  m  globular  or 
botryoidal  masses,  and 

Siliceous  sinter,  white,  translucent  to  opaque  pulverulent  accumula- 
tions and  hard  crusts,  deposited  from  the  waters  of  geysers  and  other 
hot  springs. 

Tnpolite  and  infusorial  earth  are  pulverulent  forms  of  silica  in  which 
opal  is  an  important  constituent  Tripoli  is  a  light  porous  siliceous 
rock,  supposed  to  have  resulted  from  the  leaching  of  calcareous  material 
from  a  siliceous  limestone  Infusorial  earth  represents  the  remains  of 
certain  aquatic  forms  of  microscopic  plants  known  as  diatoms 

Flint  and  Chert  are  mixtures  of  opal,  chalcedony  and  quartz 

All  vaneties  of  opal  are  infusible  and  all  become  opaque  when  heated 
When  boiled  with  caustic  alkalies  some  varieties  dissolve  easily,  while 
others  dissolve  very  slowly. 

Syntheses  — Coatings  of  material  like  opal  have  been  noted  in  glass 
flasks  containing  hydrofluosilicic  acid  that  had  not  been  opened  for 
several  years  Opal  has  also  been  obtained  by  the  slow  cooling  of  a 
solution  of  silicic  acid  in  water. 

Occurrence — The  mineral  occurs  as  deposits  around  hot  springs 
It  also  forms  veins  in  volcanic  rocks  and  is  embedded  in  certain  lime- 
stones and  slates,  where  it  is  probably  the  result  of  the  solution  of  the 
siliceous  spicules  and  shells  of  low  forms  of  Me  and  subsequent  deposi- 
tion It  also  results  from  the  solution  of  the  calcite  from  limestones 
containing  finely  divided  silica 

It  is  not  an  uncommon  alteration  product  of  silicates  It  seems  to 
have  been  deposited  from  both  cold  and  hot  water 

Localities. — Precious  opal  is  found  near  Kashan,  in  Hungary,  at 
Zimapan,  Quaretaro,  in  Mexico,  in  Honduras,  in  Queensland  and 
New  South  Wales,  Australia,  and  in  the  Faroe  Islands  Common  opal  is 
abundant  at  most  of  these  localities  and  is  found  also  in  Moravia, 
Bohemia,  Iceland,  Scotland  and  the  Hebrides  Hyalite  occurs  in  small 
quantity  at  several  places  m  New  York,  New  Jersey,  North  Carolina, 


Georgia  and  Florida,  and  common  opal,  at  Cornwall,  Perm.,  and  in 
Calaveras  Co  ,  California  Common  opal  and  vaneties  exhibiting  a  little 
fire  have  recently  been  explored  in  Humboldt  and  Lander  Counties, 
Nevada  Siliceous  sinter  is  deposited  at  the  Steamboat  Springs  in 
Nevada  and  geysente  (a  globular  form  of  the  sinter)  at  the  mouths  of  the 
geysers  in  the  Yellowstone  National  Park 

Uses  — The  precious  and  fire  opals  are  popular  and  handsome  gems 
Opahzed  wood,  i  e ,  wood  that  has  been  changed  into  opal  in  such  a 
manner  as  to  retain  its  woody  structure,  is  often  cut  and  polished  for  use 
as  an  ornamental  stone  Infusorial  earth,  a  white  earthy  deposit  of 
microscopic  shells  consisting  largely  of  opal  material,  possesses  manv 
uses  It  is  employed  in  the  manufacture  of  soluble  glass,  polishing 
powders,  cements,  etc ,  and  as  the  "  body,"  which,  saturated  with  nitro- 
glycerine, composes  dynamite,  Tripoli,  a  mixture  of  quartz  and  opal, 
is  used  as  a  wood  filler,  in  making  paint,  as  an  abrasive  and  in  the 
manufacture  of  filter  stones.  The  principal  sources  of  commercially 
valuable  opal  material  in  the  United  States  are  the  opalized  forest  in 
Apache  Co.,  Ariz ,  the  infusorial  earth  beds  at  Pope's  Creek  and  Dun- 
kirk, Md ,  various  places  in  Napa  Co ,  Cal ,  at  Virginia  City,  Nev , 
and  at  Drakesville,  N.  J.,  and  the  tnpoh  beds  in  the  neighborhood  of 
Stella,  Mo ,  and  the  adjoining  portion  of  Illinois 

Production  — The  total  quantity  of  infusonal  earth  and  tnpoh  mined 
during  1912  was  valued  at  $125,446.  The  aggregate  value  of  precious 
opal  obtained  in  1912  was  $10,925.  TluTcame  from  California  and 

Brucite  (Mg(OH)2) 

Brucite  is  the  hydroxide  of  magnesium.  It  is  a  white,  soft  mineral 
usually  occurring  in  crystals  or  in  foliated  masses 

Analyses  of  the  mineral  correspond  very  closely  to  the  formula 
Mg(OH)2  which  requires  41  38  per  cent  Mg,  27  62  per  cent  0  and  31.00 
per  cent  EkO,  though  they  usually  show  the  presence  of  small  quantities 
of  iron  and  manganese  A  specimen  from  Reading,  Perm.,  yielded: 

MgO  F^O3  MnO  H2O  Total 

67.64  82  63  3°  92  I0°  OI 

The  crystallization  of  brucite  is  hexagonal  (ditrigonal  scalenohedral), 
a  :  c=i  :  1.5208  The  crystals  are  tabular  in  habit  in  consequence  of 
the  broad  development  of  the  basal  plane  oP(oooi).  The  other  forms 
present  are  R(ioli),  -^(0441)  and  -fRCoiTj)  (Fig.  88)  The  angle 
roll  A  7ioi  =  97°  38'. 


The  cleavage  of  brucite  is  very  perfect  parallel  to  oP(ooi),  and  folia 
that  may  be  split  off  are  flexible     The  mineral  is  sectiie     Its  hardness 
is  2  5  and  its  density  2  4     Its  color  is  white,  inclining  to  bluish  and 
greenish  tints,  and  its  luster  pearly  on  oP     Brucite  is  transparent  to 
translucent      It  is   pyroelectnc    and  a  non- 
conductor of  electricity     Its  refractive  indices 
for  red  light  are   ««  i  559»  €==  *  579 

In  the  closed  tube  brucite,  like  other  hy- 
droxides, yields  water     The  mineral  is  infusi- 
ble    When  intensely  heated,  it  glows     After 
FIG   88  —Brucite  Crystal  heating,  it  reacts  alkaline     When  moistened 
with  oR,  ocoi   (<0,  R,  mfo  cobalt  mtrate  solution  and  heated,  it  turns 

Pmk» the  characterlstlc  reaction  for  magnesium 
The  pure  mineral  is  soluble  in  acids 

Brucite  resembles  m  many  respects  gypsum,  talc,  diaspore  and  some 
micas  It  is  distinguished  from  diaspore  and  mica  by  its  hardness  and 
from  talc  by  its  solubility  in  acids  Gypsum  is  a  sulphate,  hence  the 
test  for  sulphur  will  sufficiently  characterize  it 

Synthesis  — Crystals  have  been  made  by  precipitating  a  solution  of 
magnesium  chloride  with  an  alcoholic  solution  of  potash,  dissolving  the 
precipitate  by  heating  with  an  excess  of  KOH  and  allowing  to  cool 

Occurrence  and  Origin — Brucite  is  usually  associated  with  other 
magnesium  minerals  It  is  often  found  in  veins  cutting  the  rock  known 
as  serpentine,  where  it  is  probably  a  weathering  product,  and  is  some- 
times found  in  masses  in  limestone,  especially  near  its  contact  with 
igneous  rocks 

Localities — It  occurs  crystallized  in  one  of  the  Shetland  Islands,  at 
the  Tilly  Foster  Iron  Mine,  Brewster,  N  Y  ,  at  Woods  Mine,  Texas, 
Perm ,  and  at  Fritz  Island,  near  Reading,  in  the  same  State 

Gibbsite  (A1(OH)3) 

Gibbsite,  or  hydrargillite,  is  utilized  to  some  extent  as  an  ore  of  alu- 
minium It  occurs  as  crystals,  in  granular  masses,  in  stalactites  and  in 
fibrous,  radiating  aggregates 

Its  theoretical  composition  demands  6541  per  cent  AkOs  and 
34.59  per  cent  H20  Usually,  however,  the  mineral  is  mixed  with  bauxite 
(AlsO(OH)4)  and  in  addition  contains  also  small  quantities  of  iron, 
magnesium,  silicon  and  often  calcium 

Crystals  are  monodmic  with  a  :  b  :  1=1.709  *  i  :  i  918  and  £=85° 
29!'.  Their  habit  is  tabular,  Besides  the  basal  plane,  oP(ooi),  the 


two  most  prominent  forms  are  so  Poo  (I00)  ancj  aop(IIOi  Thus  the 
plates  have  hexagonal  outlines  They  ha\e  a  perfect  cleavage  parallel 
to  the  base  Twinning  is  common,  \\ith  oP(ooi)  the  twinning  plane 

The  mineral  has  a  glass}  luster  except  on  the  basal  plane  where  its 
luster  is  pearly  It  is  transparent  or  translucent,  Tvhite,  pink,  green  or 
gray  Its  streak  is  light,  its  hardness  is  2-3  and  specific  gravity  2  35 
It  is  a  nonconductor  of  electricity.  Its  refractue  indices  are  a =8 

=  15347,  7=15577 

When  heated  before  the  blowpipe  the  mineral  exfoliates,  becomes 
white,  glows  strongly  but  does  not  fuse  Upon  cooling  the  heated  mass 
is  hard  enough  to  scratch  glass  The  mineral  dissolves  slowly  but  com- 
pletely m  hot  HC1  and  in  strong  HaSOi,  and  gives  a  blue  color  when 
moistened  with  Co(NOs)2  solution  and  heated. 

Gibbsite  resembles  most  closely  bauxite,  from  which  it  is  distin- 
guished principally  by  its  structure  It  differs  from  umelhte  (p.  287), 
which  it  also  sometimes  resembles,  in  the  absence  of  phosphorus. 

Syntheses  — Crystals  of  gibbsite  have  been  made  b\  heating  on  a 
water  bath  a  saturated  solution  of  Al(OH)s  in  dilute  ammonia  until  all 
of  the  ammonia  evaporates,  and  also  by  gradually  precipitating  the 
hjdroxide  from  a  warm  alkaline  solution  by  means  of  a  slow  stream 

Occurrence  — The  mineral  rarely  occurs  in  pure  form  It  is  found  in 
veins  and  in  cavities  in  various  schistose  and  igneous  rocks.  It  is  prob- 
ably a  weathering  product  of  aluminous  silicates. 

Localities  — Gibbsite  has  been  reported  as  existing  in  small  quantities 
at  various  points  m  Europe,  near  Bombay,  India,  and  at  several  places 
in  South  America  and  Africa.  In  the  United  States  it  occurs  at  Rich- 
mond, Mass ,  at  Union  Vale,  Dutchess  Co ,  N  Y.,  and  mixed  with 
bauxite  at  several  of  the  occurrences  of  this  mineral  (see  page  186). 

Uses. — It  is  mined  with  bauxite  as  a  source  of  aluminium. 

Limonite  (Fe4O3(OH)b) 

Limomte  is  an  earthy  or  massrve  reddish  brown  mineral  whose 
composition  and  crystallization  are  but  imperfectly  known  It  is  an 
important  iron  ore  called  in  the  trade  "  brown  hematite  " 

The  analyses  of  limomte  range  between  wide  limits,  largely  because 
of  the  great  quantities  of  impurities  mixed  with  it.  The  formula  de- 
mands 59  8  per  cent  Fe,  25  7  per  cent  0  and  14.5  per  cent  water,  but  the 
percentages  of  these  constituents  found  in  different  specimens  only 
approximately  correspond  to  these  figures  Many  mineralogists  regard 



Fte  89  — Limonite  Stalactites  in  Silverbow  Mine,  Butte,  Mont    (After  W  H  Weed ) 

Era  90— Botiyoidal  Lunomte 


limomte  as  colloidal  goethite  (FeO  OH  >  with  one  molecule  or  more  of 
EfeO,  depending  upon  temperature  The  principal  impurities  are  clay, 
sand,  phosphates,  silica,  manganese  compounds  and  organic  matter 
The  great  variety  of  these  is  thought  to  be  due  to  the  lact  that  the 
hmonite,  like  other  gels,  possesses  the  po\\er  of  absorbing  compounds 
from  their  solution,  so  that  the  mineral  is  in  reaht>  a  mixture  of  col- 
loidal iron  h\  dro\ide  and  \  anous  compounds  which  differ  in  different 

The  mineral  occurs  in  stalactites  (Fig  8g\  in  botiyoidd  forms  tFig 
90),  in  concretionary  and  clay-like  masses  and  often  as  pseudomorphs 
after  other  minerals  and  after  the  roots,  lea\es  and  stems  of  trees 

Limomte  is  brown  on  a  fresh  fracture,  though  the  surface  of  mc.ny 
specimens  is  co\  ered  \uth  a  black  coating  that  is  so  lustrous  as  to  appear 
varnished  Its  streak  is  yellowish  brown  Its  hardness  is  a  little  o\  er 
5  and  its  density  about  3.7.  The  mineral  is  opaque  and  its  luster  is  dull, 
silky  or  almost  metallic  according  to  the  ph\sical  conditions  of  the  spec- 
imen. Its  index  of  refraction  is  about  25  It  is  a  nonconductor  of 

The  varieties  recognized  are.  compact,  the  stdactitic  and  other 
fibrous  forms,  ocherous,  the  brown  or  yellow  ecrthy,  impure  variety, 
bog  iron^  the  porous  variety  found  in  marshes,  pseudomorphing  leaves, 
etc ,  and  brown  clay  ironstone,  the  compact,  massive  or  nodular 

In  its  chemical  properties  limomte  resembles  goer  tie,  from  ^hich  it 
can  be  distinguished  only  with  great  difficulty  except  when  the  latter  is 
in  crystals  From  uncrystalhzed  varieties  of  goethite  it  can  usually  be 
distinguished  only  by  quantitative  analysis,  although  in  pure  specimens 
the  streaks  are  different 

Occurrence  and  Origin. — Limonite  is  the  usual  result  of  the  decom- 
position of  other  iron-bearing  minerals  Consequently,  it  is  often  found 
in  pseudomorphs.  In  almost  all  cases  'ahere  large  beds  of  the  ore  occur 
the  material  has  been  deposited  from  ferriferous  water  nch  in  organic 
substances  One  of  the  commonest  types  of  occurrence  is  "  gossan." 
In  the  production  of  this  type  of  ore,  those  portions  of  veins  carrying 
ferruginous  minerals  are  oxidized  under  the  influence  of  oxygen-bearing 
waters,  forming  a  layer  composed  largely  of  limonite  which  covers  the 
upper  portion  of  the  veins  and  hides  the  original  vein  matter  Gossan 
ores  denved  from  chalcopynte  and  pynte  are  common  in  all  regions  in 
which  these  minerals  occur  Another  type  of  limonitic  ore  comprises 
those  found  in  clays  derived  from  limestones  by  weathering  In  such 
deposits  the  ore  occurs  as  nodules  and  in  pockets  in  the  day.  Ores  of 


this  type  are  common  in  the  valleys  within  the  Appalachian  Moun- 
tains Bog  iron  ores  occur  in  swamps  and  lakes  into  which  ferruginous 
solutions  drain  The  iron  may  come  from  pynte  or  iron  silicates  in  the 
drainage  basins  of  the  lakes  or  swamps  When  carried  down  it  is  oxi- 
dized by  the  air  and  sinks  to  the  bottom 

Localities  —The  mineral  occurs  abundantly  and  in  many  different 
localities  The  most  important  American  occurrences  are  extensive 
beds  at  Salisbury  and  Kent,  Conn  ,  at  many  points  in  New  Jersey, 
Pennsylvania,  Michigan,  Tennessee,  Alabama,  Ohio,  Virginia  and 

Uses  — Although  containing  less  iron  than  hematite,  on  account  of 
its  cheapness,  and  the  ease  with  which  it  works  in  the  furnace,  brown 
hematite  is  an  important  ore  of  this  metal  The  earthy  \arieties  are 
used  as  cheap  paints 

Production  —The  yield  of  the  United  States  "  brown  hematite  " 
mines  for  1912  was  a  little  over  1,600,000  tons  Of  this  amount  the 
largest  yields  were 

Alabama  749,242  tons 

Virginia  398,833  tons 

Tennessee  171,130  tons 

The  quantity  of  ocher  produced  in  the  United  States  during  the  same 
year  amounted  to  about  15,269  tons,  valued  at  $149,289  Most  of  it 
came  from  Georgia  In  addition,  8,020  tons  were  imported.  This 
had  a  value  of  $148,300 

Bauxite  (A12O(OH)4) 

Bauxite,  or  beauxite,  like  hmomte,  is  probably  a  colloid  At  any 
rate  it  is  unknown  in  crystals  Until  recently  it  possessed  but  little 
value  It  is  now,  however,  of  considerable,  importance  as  it  is  the  prin- 
cipal source  of  the  aluminium  on  the  market 

The  mineral  is  apparently  an  hydroxide  of  aluminium  with  the  for- 
mula Al20(OH)4  or  Al20s  2H20  m  which  26  i  per  cent  is  water  and 
73  9  per  cent  alumina  (Al20s),  but  it  may  be  a  colloidal  mixture  of  the 
gibbsite  and  diaspore  (p  190)  molecules,  or  of  various  hydroxides, 
since  its  analyses  vary  within  wide  limits  A  sample  of  very  pure 
material  from  Georgia  gave  on  analysis 

A12O3  Fe203  Si02  Ti02  H2O 

62  46  81  4  72  23  31  o^ 



Bauxite  occurs  in  concretionan  grains  (Fig  91*,  m  earthy,  clay-like 
forms  and  massu  e,  usually  in  pockets  or  lenses  in  cia\  resulting  from  the 
weathering  of  limestones  or  of  s\emte  It  is  \\hite  when  pure,  but  as 
usually  found  is  yellow,  gra> ,  red  or  brown  in  color,  is  translucent  to 
opaque  and  has  a  colorless  or  very  light  streak.  Its  densitx  is  2  55 
and  its  hardness  anywhere  between  i  and  3  Its  luster  is  dull.  It  is 
a  nonconductor  of  electricity 

Before  the  blowpipe  bauxite  is  infusible     In  the  closed'tube  it  yields 

FEG.  91  — Pisohtic  Bauxite,  from  near  Rock  Run,  Cherokee  Co ,  Ala. 

water  at  a  high  temperature.  Its  powder  when  intensely  heated  with  a 
few  drops  of  cobalt  nitrate  solution  turns  blue.  The  mineral  is  with 
difficulty  soluble  in  hydrochloric  acid. 

Occurrence  and  Origin  —Bauxite  in  some  cases  may  be  a  deposit  from 
hot  alkaline  waters,  but  in  Arkansas  it  is  a  residual  ^eathenng  product 
of  the  igneous  rock,  syenite.  It  occurs  in  beds  associated  with  corundum, 
clay,  gibbsite  and  other  aluminium  minerals. 

Localities. — Large  deposits  of  the  ore  occur  at  Baux,  near  Aries, 
France,  near  Lake  Wochem,  in  Carniola,  in  Nassau;  at  Antrim,  Ire- 
land, in  a  stretch  of  country  between  Jacksonville,  Fla.,  and  Carters- 


ville,  Ga  ,  in  Saline  and  Pulaski  Counties,  Ark  ,  m  Wilkinson  Co  ,  Ga , 
and  near  Chattanooga,  Tenn 

Preparation  —The  ore  is  mined  by  pick  and  shovel,  crushed  and 
washed  It  is  then,  in  some  cases,  dried  and  broken  into  fine  particles 
The  fine  dust  is  separated  from  the  coarser  material,  and  the  latter, 
which  comprises  most  of  the  ore,  is  heated  to  400°  This  changes  the 
iron  compounds  to  magnetic  oxide  which  is  separated  electro-mag- 
neticaJly  The  concentrate  contains  about  86  per  cent  of  AfaOb  This 
is  then  purified  and  dissolved  in  a  molten  flux,  in  some  cases  cryolite, 
and  is  subjected  to  electrolysis  The  quantity  of  aluminium  made  in  the 
United  States  during  1912  was  over  65,600,000  Ib ,  valued  at  about 
$17,000,000.  The  value  of  the  aluminium  salts  produced  was  about 

Uses  — Bauxite  (or  more  properly  the  mixture  of  bauxite  and  gibbs- 
ite)  is  practically  the  only  commercial  ore  of  aluminium  which,  on 
account  of  its  lightness  and  its  freedom  from  tarnish  on  exposure,  has 
become  a  very  popular  metal  for  use  in  various  directions  It  is  em- 
ployed in  castings  where  light  weight  is  desired  and  in  the  manufacture 
of  ornaments  and  of  plates  for  interior  metallic  decorations  It  is  also 
employed  in  the  steel  industry,  and,  in  the  form  of  wire,  for  the  trans- 
mission of  electricity  The  mineral  is  also  used  in  the  manufacture  of 
aluminium  salts,  in  making  alundum  (artificial  corundum),  and  bauxite 
brick  for  lining  furnaces,  and  in  the  manufacture  of  paints  and  alloys. 

Production — The  bauxite  mined  in  the  United  States  during  1912 
amounted  to  about  159,865  tons  valued  at  $768,932,  the  greater  portion 
coming  from  Arkansas  This  is  about  two-thirds  the  value  of  the  pro- 
duction of  the  entire  world 


Psilomelane  is  probably  a  mixture  of  colloidal  oxides  and  hydroxides 
of  manganese  in  various  proportions  In  most  specimens  there  is  a 
notable  percentage  of  BaO  or  £20  present,  and  m  others  small  quantities 
of  lithium  and  thallium.  The  barium  and  potassium  components  are 
thought  to  have  been  absorbed  from  their  solutions 

The  substance  occurs  in  globular,  botryoidal,  stalactitic,  and  massive 
forms  exhibiting,  in  many  instances,  an  obscure  fibrous  structure  Its 
color  is  black  or  brownish  black  and  its  streak  brownish  black  and 
glistening.  Its  hardness  is  5  5-6  and  specific  gravity  4.2 

Psilomelane  is  infusible  before  the  blowpipe,  m  some  cases  coloring 
the  flame  green  (Ba)  and  in  others  violet  (K).  With  fluxes  it  reacts  for 


manganese.  In  the  closed  tube  it  yields  water.  It  is  soluble  in  HC1 
with  evolution  of  chlorine 

It  is  distinguished  from  most  other  manganese  oxides  and  hydroxides 
by  its  greater  hardness. 

Occurrence  — Psilomelane  occurs  in  veins  associated  with  pyrolusite 
and  other  manganese  compounds,  as  nodules  in  clay  beds,  and  as  coatings 
on  many  mangamferous  minerals  In  all  cases  it  is  probably  a  product 
of  weathering 

Locahties  — It  is  found  in  large  quantity  at  Elgersburg  in  Thuringia; 
at  Ilfeld,  Harz,  and  at  various  places  in  Saxony.  In  the  United  States 
it  occurs  with  pyrolusite  and  other  ores  of  manganese  at  Brandon,  Vt ; 
in  the  James  River  Valley,  and  the  Blue  Ridge  region  of  Virginia;  in 
northeastern  Tennessee;  at  Cartersville,  Georgia,  at  Batesville,  Arkan- 
sas, and  in  a  stretch  of  country  about  forty  miles  southeast  of  San 
Francisco,  California.  At  many  of  these  points  it  has  been  mined  as  an 
ore  of  manganese 


Wad  is  a  soft,  earthy,  black  or  dark  brown  aggregate  of  manganese 
compounds  closely  related  to  psilomelane 

It  occurs  in  globular,  botryoidal,  stalactitic,  flaky  and  porous 
masses,  which,  m  some  cases,  are  so  light  that  they  float  on  water.  It 
also  occurs  in  fairly  compact  layers  and  coats  the  surfaces  of  cracks, 
often  forming  branching  stains,  known  as  dendntes 

Wad  contains  more  water  than  psilomelane,  of  which  it  appears 
often  to  be  a  decomposition  product.  More  frequently  it  results  from 
the  weathering  of  manganiferous  iron  carbonate  It  is  particularly 
abundant  in  the  oxidized  portions  of  veins  containing  manganese  car- 
bonates and  silicates 

Wad  is  easily  distinguished  from  all  other  soft  black  minerals,  except 
pyrolusite^  by  the  reaction  for  manganese,  and  from  all  other  manganese 
compounds,  except  pyrolusite,  by  its  softness  From  pyrolusite  it  is 
distinguished  by  its  content  of  water. 

Localities— It  occurs  in  most  of  the  localities  at  which  other  man- 
ganese compounds  are  found. 


The  diaspore  group  comprises  the  hydroxides  of  aluminium,  iron 
and  manganese,  possessing  the  general  formula  R'"O(OH).  They  are 
regarded  as  hydroxides  in  which  one  of  the  hydrogens  in  BfeO  is  replaced 
by  the  group  R/7/0,  thus:  H— O— H,  water,  A10— 0— H,  diaspore  These 



three  compounds  from  a  chemical  viewpoint,  may  be  looked  upon  as  the 
acids  whose  salts  comprise  the  spinel  group  of  minerals,  which  includes 
among  others  the  three  important  ore  minerals  magnetite,  chromite  and 
frankhnite  Of  the  three  members  of  the  diaspore  group  the  manganese 
and  iron  compounds  are  valuable  ores  All  are  orthorhombic,  in  the 
rhombic  bipyramidal  class. 

Diaspore  (AIO(OH)) 

Diaspore  is  found  in  colorless  or  light  colored  crystals,  in  foliated 
masses  and  in  stalactitic  forms 

Its  composition  is  theoretically  85  per  cent  AbOs  and  15  per  cent 

Fro  92  —  Diaspore  Crystals      oo  P  So  ,  oio  (fi)  ,    oo  Pj  ,  130  (s)  ,    GO  P,  no  (m), 
210  (A),    PS5,  on   (e),  ?2,   212   (s),    ooPl,  120  (/),     «  P<j,   150  («), 

HgO,  though  analyses  show  it  to  contain,  in  addition,  usually,  some  iron 
and  silicon     A  specimen  from  Pennsylvania  yielded. 




14  84 


3  12 

Si02     Total 
i  53    100  44 

Other  specimens  approach  the  theoretical  composition  very  closely 

In  crystallization  the  mineral  is  orthorhombic  (rhombic  bipyramidal 
class),  with  a  b  .  c=  9372  .  i  :  6039  The  crystals  are  usually  pris- 
matic, though  often  tabular  parallel  to  oo  P  56  (oio)  The  principal 
planes  observed  on  them  are  oo  Poo  (oio),  a  series  of  prisms  as 
ooP(no),  oo  Pa (210),  °oP3(i3o),  the  dome  PQ&(OII)  and  several 
pyramids  (Fig.  92)  The  planes  of  the  prismatic  zone  are  often  ver- 
tically striated  The  angle  no  A  i  Io-86°  if 

The  cleavage  of  diaspore  is  very  distinct  parallel  to  the  brachy- 
pmacoid.  Its  fracture  is  conchoidal  and  the  mineral  is  very  brittle, 
Its  hardness  is  about  6  5  and  density  3  4  The  luster  of  the  mineral  is 
vitreous,  except  on  the  cleavage  surface,  where  it  is  pearly.  Its  color 


varies  widely,  though  the  tint  is  always  light  and  the  streak  colorless 
The  predominant  shades  are  bluish  white,  grayish  white,  yellowish  or 
greenish  white     The  mineral  is  transparent  or  translucent     It  is  a 
nonconductor  of  electricity     Its  refractive  indices  for  yellow  light  are 
a=  1702,  j8=i  722,  7  =  1  750 

In  the  closed  tube  diaspore  decrepitates  and  gives  off  water  at  a  high 
temperature  It  is  infusible  and  insoluble  in  acids.  When  moistened 
with  a  solution  of  cobalt  nitrate  and  heated  it  turns  blue,  as  do  all  other 
colorless  aluminium  compounds 

In  appearance,  diaspore  closely  resembles  Irucite  (Mg(OH)s),  from 
which  it  may  be  distinguished  by  its  greater  hardness  and  its  aluminium 
reaction  with  cobalt  nitrate 

Synthesis  — Crystal  plates  of  diaspore  have  been  made  by  heating  at 
a  temperature  of  less  than  500°,  an  excess  of  amorphous  AfeQs  in  sodium 
hydroxide,  enclosed  in  a  steel  tube  At  a  higher  temperature  corundum 

Occurrence — Diaspore  occurs  as  crystals  implanted  on  corundum 
and  other  minerals,  and  on  the  walls  of  rocks  in  which  corundum  is 
found  It  is  probably  in  most  cases  a  decomposition  product  of  other 
aluminium  compounds 

Localities — In  Ekaterinburg,  Russia,  it  is  associated  with  emery. 
At  Schemnitz,  Hungary,  it  occurs  in  veins  It  is  found  also  in  the 
Canton  of  Tessin,  in  Switzerland,  at  various  places  in  Asia  Minor,  and 
on  the  emery-bearing  islands  of  the  Grecian  Archipelago.  In  the 
United  States  it  is  associated  with  corundum,  at  Newlin,  Chester  Co , 
Penn ,  with  emery  at  Chester,  Mass ,  at  the  Culsagee  corundum  mine, 
near  Franklin,  N  C  ,  and  at  other  corundum  mines  in  the  same  State. 

Manganite  (MnO(OH)) 

Manganite  usually  occurs  in  groups  of  black  columnar  or  prismatic 
crystals  and  in  stalactites. 

The  formula  MnO(OH)  requires  27  3  per  cent  0,  62  4  per  cent  Mn 
and  10  3  per  cent  water,  or  89  7  per  cent  MnO  and  10  3  per  cent  water. 
In  addition  to  these  constituents,  the  mineral  commonly  contains  also 
some  iron,  magnesium,  calcium  and  often  traces  of  other  metals.  An 
analysis  of  a  specimen  from  Langban,  in  Sweden,  yielded: 

Mn2O3         Fe203         MgO      CaO        H2O        Total 
88  51  23  i  51         62         9  80       100  67 

The  orthorhombic  crystals  of  the  mineral  have  an  axial  ratio  a  :  i :  c 
=  8441  :  i  :  ,5448  The  crystals  are  nearly  all  columnar  with  a  series 



of  pnsms,  among  which  are  oo  P^io)  and  oo  P(uo),  and  the  two  lateral 
pinacoids  oo  P  06  (oio)  and  8  P  a  (100)  terminated  by  oP(ooi)  or  by 
the  domes  P  06  (on),  P  06  (101),  and  pyramids  (Figs  93  and  94)  Cru- 
ciform and  contact  twins,  with  the  twinning  plane  P  oo  (on),  are  not 
uncommon  (Fig  95)  The  prismatic  surfaces  are 
vertically  striated  and  the  crystals  are  often  in 
bundles  The  angle  no  A  iTo=8o°  20' 

Cleavage  is  well  defined  parallel  to  oo  P  06  (oio) 
and  less  perfectly  developed  parallel  to  ooP(no) 
The  fracture  is  uneven     The  luster  of  the  mineral 
is  brilliant,  almost  metallic     Its  color  is  iron-black 
and  its  streak  reddish  brown  or  nearly  black     It 
is  usually  opaque  but  in  very  thin  splinters  it  is 
sometimes  brown  by  transmitted  light.    Its  hard- 
ness is  4  and  density  about  4  3.    The  mineral  is 
a  nonconductor  of  electricity 
Mangamte  yields  water  in  the  closed  tube  and  colors  the  borax  bead 
amethyst  m  the  oxidizing  flame  of  the  blowpipe.    In  the  reducing  flame, 
upon  long-continued  heating,  this  color  disappears     The  mineral  dis- 
solves in  hydrochloric  acid  with  the  evolution  of  chlorine.    It  is  dis- 

FIG  93  — Mangamte 
Crystal  with  ooP, 
no(w),  oP,ooi  (c) 
and  P  55  ,  ioi  («) 

FIG  94  — Group  of  Prismatic  Mangamte  Crystals  from  Lfeld,  Hare. 

tinguished  from  other  manganese  minerals  by  its  hardness  and  crystal- 

By  loss  of  water  mangamte  passes  readily  into  pyrolusite  (MnCfe). 
It  also  readily  alters  into  other  manganese  compounds 

Synthesis.— Upon  heating  for  six  months  a  mixture  of  manganese 
chloride  and  damn  caarbonate  fine  crystals  like  those  of  mangamte 


have  been  obtained  Their  composition,  howe\er,  was  that  of  haus- 
manmte,  indicating  that  \\hile  mangamte  was  produced,  it  was  changed 
to  hausmanmte  during  the  process. 

Occurrence,  Localities  and  Origin  — Man- 
gamte occurs  in  veins  in  old  volcanic  rocks, 
and  also  in  limestone  It  is  found  at  Ilfeld 
in  the  Harz,  at  Ilmenau  in  Thurmgia,  and 
at  Langban  in  Sweden,  in  handsome  cns- 
tals  In  the  United  States  it  occurs  at  the 
Jackson  and  the  Lucie  iron  mines,  Xegaunee, 

Mich ,  and  in   Douglas   Co ,  Colo      It  is    _ 

,         ,        ,      .      A  :  „         FIG   05—  Manoamte  Crvstal 

also  abundant  at  ^arlous  places   m  New       Tvvmned  abjut  P^('QII^ 

Brunswick  and  Nova  Scotia  In  all  cases  The  torms  are  =c  P  notmj, 
it  is  a  residual  product  of  the  weathering  of  =cP3,i2o./;andP3  31315) 
manganese  compounds. 

Uses  — Mangamte  is  used  in  the  production  of  manganese  compounds. 
As  mined  it  is  usually  mixed  with  pyrolusite,  this  being  the  most  im- 
portant portion  of  the  mixture 

Goethite  (FeO(OH)) 

This  mineral,  though  occasional!}-  found  m  blackish  brown  crystals, 
usually  occurs  in  radiated  globular  and  botryoidal  masses  Analyses 
of  specimens  from  Maryland,  and  from  Lostwithiel,  in  Cornwall,  gave- 

Fe20s        Mn2Q3        H2O         SiCb  Total 

Maryland  86  32  10  So          2  88  too  oo 

Lostwithiel  89  55  16          10  07  28  100  06 

The  formula  FeO(OH)  demands  89.9  per  cent  Fe2Qs  and  10  i  per  cent 
H2O  or  62.9  per  cent  Fe,  27  o  per  cent  0  and  10  i  per  cent  HaO 

Like  diaspore  and  mangamte,  goethite  is  orthorhornbic,  its  axial 
ratio  being  a  :  b  :  c  =  9185  :  i :  .6068  Its  crystals  are  prismatic  or 
acicular  with  the  prisms  plainly  striated  vertically  The  forms  observed 
are  commonly  oo  P  06  (oio),  QO  PS(2io\  oo  P(no),  P  06  (on)  and  P(rii). 
The  angle  no  A  1*10=85°  8'. 

The  deavage  of  goethite  is  perfect  parallel  to  oo  P  06  (oio)  and  its 
fracture  uneven  Its  hardness  is  5  and  density  about  4.4.  Its  color  is 
usually  yellowish,  reddish  or  blackish  brown  and  its  luster  almost 
metallic  In  thin  splinters  it  is  often  translucent  with  a  blood-red  color 
and  a  refractive  index  of  about  2  5  Its  streak  is  brownish  yellow.  It 
is  an  electric  nonconductor. 


The  chemical  reactions  of  the  mineral  are  about  the  same  as  those  of 
hematite,  except  that  it  yields  water  when  heated  in  the  closed  tube 
By  this  reaction  it  is  easily  distinguished  from  the  fibrous  varieties  of 
hematite,  as  it  is  also  by  its  streak 

Synthesis — Needles  of  goethite  are  produced  by  heating  freshly 
precipitated  iron  hydroxide  for  a  long  time  at  100° 

Occurrence  and  Localities  — Goethite  is  usually  associated  with  other 
ores  of  iron,  especially  in  the  upper  portion  of  veins,  -where  it  is  produced 
by  weathering.  It  is  found  near  Siegen  in  Nassau,  near  Bristol  and 
Clifton,  England,  and  in  large,  fine  crystals  at  Lostwithiel  and  other 
places  in  Cornwall 

In  the  United  States  it  occurs  in  small  quantity  at  the  Jackson  and 
the  Lucie  hematite  mines  in  Negaunee,  Mich  ,  at  Salisbury,  Conn  , 
at  Easton,  Penn  ,  and  at  many  other  places 

Uses  — Goethite  is  used  as  an  ore  of  iron,  but  in  the  trade  it  is  classed 
with  limomte  as  brown  hematite 


MOST  of  these  compounds  are  salts  of  the  comparative!}  uncommon 
acids  HA1O2,  HFeOo  and  HCrCb,  \\hich  may  be  regarded  as  metaacids 
derived  from  the  corresponding  normal  acids  by  the  abstraction  of  water, 
thus.  HsAlOs—  H2O=HAlOo  There  are  onh  a  few  minerals  belong- 
ing to  the  group  but  they  are  important  One,  magnetite,  is  an  ore  of 
iron,  another,  chronute,  is  the  principal  ore  of  chromium  and  two  others 
are  utilized  as  gems  Most  of  them  are  included  in  the  mineral  group 
known  as  the  spmels  (Compare  p  189  ) 

That  there  is  a  manganese  acid  corresponding  to  the  metaacids  of  AI, 
Fe  and  Cr  is  indicated  by  the  fact  that  in  some  of  the  spinels  manganese 
replaces  some  of  the  fernc  iron,  as,  for  example,  in  frankhmte.  This 
suggests  that  this  mineral  is  an  isomorphous  mixture  of  a  metafernte 
and  a  salt  of  the  corresponding  manganese  acid  (HMnCb)  This  may 
be  regarded  as  derived  from  the  hydroxide,  MnfOH)s,  by  abstraction 
of  H2O,  thus-  H3Mn03-H2CMHMnO.>.  But  there  are  other  man- 
ganous  acids  Normal  manganous  acid  is  MnfOH)^,  or  H4Mn(>4  If 
from  this  one  molecule  of  water  be  abstracted,  there  remains  H2^InOs, 
the  metamanganous  acid  The  manganous  salt  of  the  normal  acid, 
Mn2MnQi,  occurs  as  the  mineral,  hausmannite,  and  the  corresponding 
salt  of  the  metaacid,  MnMnOs,  as  the  mineral,  braunite. 


The  spinels  are  a  group  of  isomorphous  compounds  that  may  be 
regarded  as  salts  of  the  acids  AIO(OH),  MnO(OH),  CrO(OH)  and 
FeO(OH),  in  which  the  hydrogen  is  replaced  by  Mg,  Fe  and  Cr. 

Al—  0—  CX 
Thus,  spinel,  Mg-  AfeQ*  may  be  regarded  as  ||  yMg,   magnetite, 

Fe—  0—  Ov  Cr—  O-Ov 

Fe3O4,  as  II  >Fe;  clromite,  FeCx&O*,  as  ||  )>Fe,  and 

Fe-O-(X  Cr-O-CK 

(Fe  Mn)-O-<X 

frankhmte,  as    I      I  y>(Zn-Mn  Fe).  Chemical  compounds  of 

(Fe  Mn)-0-CK 




this  general  type  are  fairly  numerous,  but  only  a  few  occur  as  minerals 
The  most  important  are  the  three  important  ores  mentioned  above, 
spinel  is  of  some  value  as  a  gem  btone 

The  spinels  crystallize  in  the  holohedral  divi- 
sion of  the  isometric  system  (hexoctahedral  class), 
in  well  defined  crystals  that  are  usually  combina- 
tions of  0(ui)  and  ooO(no),  with  the  addition  on 
some  of  ooQoo  (100),  303(311),  202(211),  50^(531), 
etc  Contact  twins  are  so  common  with  0  the 
twinning  plane,  that  this  type  of  twinning  is  often 
referred  to  as  the  spinel  twinning  (Fig  96). 

FIG  96 

Spinel  Twin 

The  complete  list  of  the  known  spinels  is  as  follows. 


Ceylomte  (pleonaste) 













(Mg  Fe)(A102)2 

Mg((Al  Fe)02)2 

(Mg  Fe)((Al  Fe-Cr)02)2 



(Zn  Fe  Mn)((Al  Fe)02)2 

(Zn  Fe  Mg)  ((Al  Fe)O2)2 



(Fe  ZnMn)((Fe  Mn)O2)2 

(Mn  Mg)((Fe  Mn)02)2 

(Fe  Mg)(Cr  Fe)02)2 

Spinel  (Mg(AlO2)2) 

Ordinary  spinel  is  the  magnesian  alummate,  which,  when  pure,  con- 
tains 28  3  per  cent  MgO  and  71  7  per  cent 
AfeOa     Usually,  however,  there  are    present 
admixtures  of  the  other  isomorphs  so  that 
analyses  often  indicate  Fe,  Al  and  Cr 

The  mineral  usually  occurs  in  isolated 
simple  crystals,  rarely  in  groups  The  forms 
observed  on  them  are  0(m),  ooO(no)  and 
303(311),  and  rarely  oo  0  oo  (100)  (Fig  97) 

The  pure  magnesium  spinel  is  colorless  or  FlG    97— Spinel    Crystal 
some  shade  of  pink  or  red,  brown  or  blue,  and      J^'Q  (^r£)"° 
is  usually  transparent  or  translucent,  though          an   3  3'  3I1 
opaque  varieties  are  not  rare    Its  streak  is  white    It  possesses  a  glassy 


luster,  and  a  conchoidal  fracture,  but  no  distinct  cleavage  Its  hard- 
ness is  8  and  its  density  3  5-3  6  Its  refractive  indices  \ary  with  the 
color  n  for  yellow  light  is  i  7150  for  red  spinel  and  i  7201  for  the  blue 

The  mineral  is  infusible  before  the  blowpipe  and  is  unattacked  by 
acids  It  yields  the  test  for  magnesia  with  cobalt  solution 

Spinel  is  easily  distinguished  from  most  other  minerals  by  its  cns- 
tallization  and  hardness  It  is  distinguished  from  pale-colored  garnet 
by  its  blowpipe  reactions,  especially  its  infusibility,  and  its  failure  to 
respond  to  the  test  for  Si02 

The  best  known  varieties  are: 

Precious  spinel,  which  is  the  pure  magnesian  aluminate.  It  is  trans- 
parent and  colorless  or  some  light  shade  of  red,  blue  or  green.  The 
bright  red  variety  is  known  as  ruby  spinel  and  is  used  as  a  gem  Its 
color  is  believed  to  be  due  to  the  presence  of  chromium  oxide  It  is 
easily  distinguished  from  genuine  ruby  by  the  fact  that  it  is  not  doubly 
refracting  and  not  pleochroic. 

The  best  ruby  spinels  come  from  Ceylon,  where  they  occur  loose  in 
sand  associated  with  zircon,  sapphire,  garnet,  etc. 

Common  spinel  differs  from  precious  spinel  m  that  it  is  translucent. 
It  usually  contains  traces  of  iron  and  alumina. 

Both  these  varieties  of  spinel  occur  in  metamorphosed  limestones 
and  crystalline  schists. 

Syntheses  —  The  spinels  have  been  made  by  heating  a  mixture  of 
AkOs  and  MgO  with  boracic  acid  until  fusion  ensues,  and  by  heating 
Mg(OH)2  with  AlCls  in  the  presence  of  water  vapor 

Origin  —  Spinel  has  been  described  as  an  alteration  product  of  corun- 
dum and  garnet  It  is  also  a  primary  component  of  igneous  rocks  and 
a  product  of  metamorphism  in  rocks  nch  in  magnesium 

Uses  —  Only  the  transparent  ruby  spinels  have  found  a  use.  These 
are  employed  as  gems 

Ceylonite,  or  pleonaste,  is  a  spinel  in  which  a  portion  of  the  Mg 
has  been  replaced  by  Fe,  i  e  ,  is  an  isomorphous  mixture  of  the  magne- 
sian and  iron  aluminates,  thus  ((Mg  Fe)(AlO2)2)  It  is  usually  black 
or  green  and  translucent,  and  has  a  brownish  or  dark  greenish  streak 
and  a  density  =3  5-3  6 

The  analysis  of  a  sample  separated  from  an  igneous  rock  in  Madison 
Co  ,  Mont.,  gave, 

A12O3        FeO      MgO     CraOs     Fe^     MnO     CaO     SiOa    Total 
62  09      17  56     15  61       2  62        2  10        tr  16         55    100  69 


Ceylomte  occurs  in  igneous  rocks  m  the  Lake  Laach  region, 
Germany,  and  m  the  Piedmont  district,  Italy  and  elsewhere,  m  meta- 
morphosed limestones  at  Warwick  and  Amity,  N  Y  ,  m  the  limestone 
blocks  enclosed  in  the  lava  of  Vesuvius,  and  m  dolomite  metamor- 
phosed by  contact  action  at  Monzoni,  Tyrol 

Picotite,  or  chrome  spinel,  is  a  \anety  intermediate  between  spinel 
proper  and  chromite  Its  composition  may  be  represented  by  the 
formula  (Mg  Fe)((Al  Fe  Cr)O2)2  It  occurs  only  m  small  crystals  in 
basic  igneous  rocks  and  in  a  few  crystalline  schists  Density =4  i 

Magnetite  (Fe(FeO2)2) 

Magnetite,  the  ferrous  fernte,  the  empirical  formula  of  which  is 
FesO-i,  is  a  heavy,  black,  magnetic  mineral  which  is  utilized  as  one  of 
the  ores  of  iron 

The  pure  mineral  consists  of  72  4  per  cent  Fe  and  27  6  per  cent  0 
Most  specimens,  however,  contain  also  some  Mg  and  many  contain  small 
quantities  of  Mn  or  Ti  A  selected  sample  of  magnetite  from  the  Eliza- 
beth Mine,  Mt  Hope,  New  Jersey,  analyzed  as  follows 

Fe2O3       FeO       Si02      Ti02     A1203     MgO      CaO      Other     Total 
65  26      30  20      i  38      i  09         55         10         68  73      99  99 

Magnetite  occurs  in  crystals  that  are  usually  octahedrons  or  dodeca- 
hedrons, or  combinations  of  the  two  ,  Other  forms  are  rare  Twins 
are  common  The  mineral  occurs  also  as  sand 
and  in  granular  and  structureless  masses  When 
the  dodecahedron  is  present,  its  faces  are  fre- 
quently striated  parallel  to  the  edge  between 
ooO(no)  and  0(ui)  (Fig  98) 

Magnetite  is  black  and  opaque  and  its  streak  FIG  98  —Magnetite 
is  black  It  has  an  uneven  or  a  conchoidal  f rac-  Crystal,  with  w  o 
ture,  but  no  distinct  cleavage  Its  hardness  is  (llo)  and  °  (l3CI)» 
S.S^anddeM1ty49-5*  It  is  strongly  attracted  f™* 
by  a  magnet  and  in  many  instances  it  exhibics  and  in 
polar  magnetism 

The  mineral  is  infusible  before  the  blowpipe  Its  powder  dissolves 
slowly  in  HC1,  and  the  solution  reacts  for  ferrous  and  ferric  iron 

Magnetite  is  easily  recognized  by  its  color,  magnetism,  and  hardness 

The  mineral  weathers  to  lunomte  and  hematite  and  occasionally  to 
the  carbonate,  sidente, 


Syntheses. — Crystals  have  been  made  by  cooling  iron-bearing  silicate 
solutions,  treating  heated  ferric  hydroxide  \\ith  HC1,  and  by  fusing 
iron  oxide  and  borax  with  a  reducing  flame 

Occurrence  end  Ongm. — The  mineral  occurs  as  a  constituent  of 
many  igneous  rocks  and  crystalline  schists,  and  in  lenses  embedded  in 
rocks  of  many  kinds  It  also  constitutes  veins  cutting  these  rocks 
and  as  irregular  masses  produced  b\  the  deh\  dration  and  deoxidation 
of  hematite  and  limomte  under  the  influence  of  metamorphic  processes. 
It  occurs  also  as  little  grains  among  the  decomposition  products  of 
iron-bearing  silicates,  such  as  olmne  and  hornblende. 

The  larger  masses  are  either  segregations  from  igneous  magmas  or 
deposits  from  hot  solutions  and  gases  emanating  from  them. 

Localities  — The  localities  at  \\hich  magnetite  has  been  found  are  so 
numerous  that  only  those  of  the  greatest  economic  importance  may  be 
mentioned  here.  In  Norway  and  Sweden  great  segregated  deposits  are 
\\orked  as  the  principal  sources  of  iron  in  these  countries.  In  the 
United  States  large  lenses  occur  in  the  limestones  and  siliceous  crys- 
talline schists  in  the  Adirondacks,  New  York,  and  in  the  schists  and 
granitic  rocks  of  the  Highlands  in  New  Jersey  Great  bodies  are  mined 
also  at  Cornwall,  and  smaller  bodies  at  Cranberry,  and  in  the  Far 

Extraction  — The  magnetite  is  separated  from  the  rock  with  which  it 
occurs  by  crushing  and  exposing  to  the  action  of  an  electro-magnet. 

Production  — The  total  amount  of  the  mineral  mined  m  the  United 
States  during  1912  was  2,179,500  tons,  of  which  1,110,345  tons  came 
from  New  York,  476,153  tons  from  Pennsylvania,  and  364,673  tons 
from  New  Jersey. 

FrankEnite  ((Fe-Zn  Ua)((Fe-Hn)O2)2) 

Franklinite  resembles  magnetite  in  its  general  appearance.  It  is  an 
ore  of  manganese  and  zinc 

It  differs  from  magnetite  m  containing  Mn  in  place  of  some  of  the 
ferric  iron  in  this  mineral  and  Mn  and  Zn  in  place  of  some  of  its  ferrous 
iron.  Since  it  is  an  isomorphous  mixture  of  the  iron,  zinc  and  manganese 
salts  of  the  iron  and  manganese  acids  of  the  general  formula  R"'0(OH), 
its  composition  varies  within  wide  limits  The  franklinite  from  Mine 
Hill,  N.  J ,  contains  from  39  per  cent  to  47  per  cent  Fe,  10  per  cent  to 
19  per  cent  Mn  and  6  per  cent  to  18  per  cent  Zn  A  specimen  from 
Franklin  Furnace,  N  J.,  contained, 

Fe203       MnO         ZnO       MgO       CaO       SiOa         HsO      Total 
66  58       9  96         so  77         34         -43          -72  -71       99-5* 


Its  crystals  are  usually  octahedrons,  sometimes  modified  by  the  do- 
decahedron and  occasionally  by  other  forms  The  mineral  occurs  also 
in  rounded  grams,  in  granular  and  in  structureless  masses 

It  is  black  and  lustrous  and  has  a  dark  brown  streak  Its  fracture 
and  cleavage  are  the  same  as  for  magnetite  It  is  only  very  slightly 
magnetic  It  has  a  hardness  of  6  and  a  density  of  5  15 

The  mineral  is  infusible  before  the  blowpipe  When  heated  on 
charcoal  it  becomes  magnetic  When  fused  with  Na2COa  in  the  oxidizing 
flame  it  gives  the  bluish  green  bead  characteristic  of  manganese  Its 
fine  powder  mixed  with  Na2COa  and  heated  on  charcoal  yields  the  white 
coating  of  zinc  oxide  which  turns  green  when  moistened  with  Co(N03)2 
solution  and  again  heated 

Franklinite  is  distinguished  from  most  minerals  by  its  color  and  crys- 
tallization and  from  magnetite  and  clromite  by  its  brown  streak  and 
by  its  reactions  for  Mn  and  Zn  It  is  also  characterized  by  its  associa- 
tion with  red  zmcite  and  green  or  pink  willemite  (p  306) 

Synthesis — Crystals  of  franklmite  have  been  made  by  heating  a 
mixture  of  FeCla,  ZnCb  and  CaO  (lime) 

Occurrence  and  Origin  — Franklimte  occurs  at  only  a  few  places  Its 
most  noted  localities  are  Franklin  Furnace  and  Sterling  Hill,  N  J  ,  where 
it  is  associated  in  a  white  crystalline  limestone  with  zmcite,  willemite 
and  other  zinc  and  manganese  compounds  The  deposit  is  supposed 
to  have  been  produced  by  the  replacement  of  the  limestone  through  the 
action  of  magmatic  waters  and  vapors. 

Uses. — The  mineral  is  utilized  as  an  ore  of  manganese  and  zinc 
The  ore  as  mined  is  crushed  and  separated  into  parts,  one  of  which 
consists  largely  of  franklmite  This  is  roasted  with  coal,  when  the  zinc 
is  driven  off  as  zinc  oxide  The  residue  is  smelted  in  a  furnace  producing 
spiegeleisen,  which  is  an  alloy  of  iron  and  manganese  used  in  the  man- 
ufacture of  certain  grades  of  steel 

Production — The  quantity  of  this  residuum  produced  in  1912  was 
104,670  tons,  valued  at  $314,010 

Chromite  (Fe(CrO2)2) 

Chromite,  or  chrome-iron,  is  the  principal  ore  of  chromium.  It 
resembles  magnetite  and  frankhnite  in  appearance  It  occurs  in  iso- 
lated crystals,  in  granular  aggregates,  and  in  structureless  masses. 

Chemically,  it  is  a  ferrous  salt  of  metachromous  acid,  of  the  theoret- 
ical composition  Cr20a=68  per  cent  and  FeO=32  per  cent,  but  it  usually 
contains  also  small  quantities  of  Al^Oa,  CaO  and  MgO  An  analysis  of 


a  specimen  from  Chorro  Creek,  California,  after  making  corrections  for 
the  presence  of  some  serpentine,  yielded 

Cr203         A1203         Fe203  FeO  MgO        MnO      Total 

56  96          12  32  3  81  12  73          14  02  16        100  oo 

Its  crystals  are  usually  simple  octahedrons,  but  they  are  not  as 
common  as  those  of  the  other  spinels 

Its  color  is  brownish  black  and  its  streak  brown  It  has  a  conchoidal 
or  uneven  fracture  and  no  distinct  clea\age  It  is  usually  nonmag- 
netic, but  some  specimens  sho\\  slight  magnetism  because  of  the  ad- 
mixture of  the  isomorphous  magnetite  molecule  Its  hardness  is  5  5 
and  its  density  4  5  to  4  8 

The  mineral  is  infusible  before  the  blowpipe  It  gives  the  chromium 
reaction  with  the  beads  If  its  powder  is  fused  with  niter  and  the  fusion 
treated  with  water,  a  yellow  solution  of  KoCrO4  results  When  fused 
with  NagCOs  on  charcoal  it  yields  a  magnetic  residue. 

Chromite  is  easily  distinguished  from  all  other  minerals  but  ptco- 
tite  by  its  crystallization  and  its  reaction  for  chromium.  It  is  distin- 
guished from  picotite  by  its  inferior  hardness  and  its  higher  specific 

Synthesis  — Crystals  have  been  made  by  fusing  the  proper  constit- 
uents with  boric  acid  and  after  fusion  distilling  off  the  boric  acid. 

Occurrence  and  Origin  — Chromite  occurs  principally  in  olivine  rocks 
and  in  their  alteration  product — serpentine  The  mineral  is  found  not 
only  as  crystals  embedded  in  the  rock  mass,  but  also  as  nodules  in  it 
and  as  veins  traversing  it  It  is  probably  in  all  cases  a  segregation  from 
the  magma  producing  the  rock  In  a  few  places  the  mineral  occurs 
in  the  form  of  sand  on  beaches 

Localities  — It  is  widely  spread  through  serpentine  rocks  at  many 
places,  notably  in  Brussa,  Asia  Minor;  at  Banat  and  elsewhere  in 
Norway;  at  Solnkive,  in  Rhodesia,  in  the  northern  portion  of  New 
Caledonia,  at  various  points  in  Macedonia,  in  the  Urals,  Russia;  in 
Beluchistan  and  Mysore,  India 

In  the  United  States  the  mineral  is  known  at  several  points  in  a  belt 
of  serpentine  on  the  east  side  of  the  Appalachian  Mountains,  and  at 
many  points  in  the  Rocky  Mountains,  the  Sierra  Nevada  and  the  Coast 
Ranges  It  has  been  mined  at  Bare  Hills,  Maryland,  in  Siskiyou, 
Tehama  and  Shasta  Counties,  Colorado,  in  Converse  County,  Wyoming; 
and  in  Chester  and  Delaware  Counties,  Pennsylvania,  and  in  1914, 
some  was  washed  from  chrome  sand  at  Baltimore,  Maryland. 


Metallurgy  —The  mineral  is  mined  by  the  usual  methods  and  con- 
centrated, or,  if  in  large  fragments,  is  crushed  It  is  then  fused  with 
certain  oxidizing  chemicals  and  the  soluble  chromates  are  produced. 
Or  the  ore  is  reduced  with  carbon  yielding  an  alloy  with  iron  The 
metal  is  produced  by  reduction  of  its  oxide  by  metallic  aluminium  or  by 
electrolysis  of  its  salts 

jjses  — Chromite  is  the  sole  source  of  the  metal  chromium,  which  is 
the  chrome-iron  alloy  employed  m  the  manufacture  of  special  grades 
of  steel  Chromium  salts  are  used  in  tanning  and  as  pigments  The 
crude  ore,  mixed  with  coal-tar,  kaolin,  bauxite,  or  some  other  ingredient, 
is  molded  into  bricks  and  burned,  after  which  the  bricks  are  used  as 
linings  in  metallurgical  furnaces.  These  bricks  stand  rapid  changes  of 
temperature  and  are  not  attacked  by  molten  metals 

Production — The  annual  production  of  chromite  in  the  world  is 
now  about  100,000  tons,  of  which  Rhodesia  produces  about  J,  New 
Caledonia  about  |  and  Russia  and  Turkey  about  \  each  The  produc- 
tion of  the  United  States  in  1912  was  201  tons,  valued  at  $2,753.  All 
came  from  California.  The  imports  in  the  same  year  were  53,929  tons, 
worth  $499,818. 


Chrysoberyl  is  a  beryllium  alummate,  the  composition  of  which  is 
analogous  to  that  of  the  spinels  It  may  be  written  Be02(A10)2.  Al- 
though theoretically  it  should  contain  19  8  per  cent  BeO  and  80  2  per 
cent  AkOa,  analyses  of  nearly  all  specimens  show  the  presence  also  of 
iron  and  magnesium 

The  mineral  differs  from  spinel  in  crystallizing  in  the  orthorhombic 
system  (bipyramidal  class)  Its  axial  ratio  is  .4707  :  i  :  5823  The 
principal  forms  observed  on  crystals  are  P(in),  ooP  06(100), 
oo  P  oo  (oio),  P  06  (on),  oo  P2(i2o)  and  2P?(i2i)  (Fig  99)  The  crystals 
are  often  twins  (Fig  100),  trillings  or  sixlmgs,  with  3?  06  (031)  the 
twinning  plane,  forming  pseudohexagonal  groupings  (Fig  101)  Sim- 
ple crystals  are  usually  tabular  parallel  to  oo  P  So  (100),  which  is  striated 
vertically  Consequently,  in  twins  this  face  exhibits  stnations  arranged 
feather-like.  The  angle  no  A  iTo=5o°  21'. 

The  deavage  of  chrysoberyl  is  distinct  parallel  to  Poo  (on),  and 
indistinct  parallel  to  oo  P  06  (oio)  and  oo  P  56  (100)  Its  fracture  is 
uneven  or  conchoidal.  Its  color  is  some  shade  of  light  green  or  yellow 
by  reflected  light.  It  is  transparent  or  translucent  and  in  some  cases  is 
distinctly  red  by  transmitted  light.  It  is  strongly  pleochroic  m  orange, 



green  and  red  tints.    The  mineral  is  brittle,  has  a  hardness  of  8  5  and  a 
density  of  about  3  6     Its  refractive  indices  are  a=i  7470,  j5=i  7484, 

Four  distinct  varieties  are  recognized 

Ordinary,  pale  green,  translucent 

Gem,  yellow  and  transparent 

Alexandrite,  emerald-green  in  color,  but  red  by  transmitted  light, 
transparent,  usually  in  twins  Used  as  a  gem 

Cat's-eye,  a  greenish  variety  exhibiting  a  play  of  colors  (chatoyancy ) 

Before  the  blowpipe  the  mineral  is  infusible  It  yields  the  Al  reac- 
tion with  Co(NOs)2,  but  otherwise  is  only  slightly  affected  by  the  flame 
It  is  insoluble  in  acids 

Chrysoberyl  is  characterized  by  its  crystallization  and  great  hard- 

FIG  99 

FIG  ioo 

FIG  101 

FIG  99  — Chrysoberyl  Crystal  with  oo  P  GO  3 100  (a),  oo  P  55 ,  oio  (b),    oo  P7, 120  (s), 

2&2t  121  («),  P,  in  (o)  and  P  oo ,  on  (i). 
FIG  100  — Chrysoberjl  Thinned  about  3?  So  (031) 
FIG  1 01  — Chrysobeiyl  Pseudohexagonal  Sixlmg  Twinned  about  3?  5  (031) 

ness  It  most  closely  resembles  the  beryllium  silicate,  beryt,  in  appear- 
ance, but  is  easily  distinguished  from  this  by  its  crystallization. 

Synthesis. — Crystals  have  been  made  by  fusing  BeO  and  AkOs 
with  boric  acid  and  then  distilling  off  the  boric  acid 

Occurrence  and  Origin  — Chrysoberyl  is  found  principally  in  granites 
and  crystalline  schists  and  as  grains  in  the  sands  produced  by  the  erosion 
of  these  rocks  In  its  original  position  the  mineral  is  a  separation 
from  the  magma  that  produced  the  rocks. 

Localities. — Its  best  known  localities  are  in  Minas  Geraes,  Brazil, 
near  Ekaterinburg,  Ural;  in  the  Mourne  Mts,,  Ireland,  at  Haddam, 
Conn  ,  at  Greenfield,  N.  Y.;  at  Orange  Summit,  N.  Hamp.;  and  at 
Norway  and  Stoneham,  Me.  The  alexandrite  comes  from  Ceylon,  where 
it  occurs  as  pebbles,  and  from  the  Urals. 



Braunite  (MnMnOs)  occurs  massive  and  in  crystals.  The  latter 
are  tetragonal  (ditetragonal  bipyramidal  class),  'with  a  c—i  9922, 
They  are  usually  simple  bipyramids  P(in)  Because  of  the  nearly 
equal  value  of  a  and  c  all  crystals  are  isometric  in  habit  The  angle 
iiiAii"i  70°  7'  Twins  are  common,  with  POO(IOI)  the  twinning 
plane  Cleavage  is  perfect  parallel  to  P(III) 

The  mineral  is  brownish  black  to  steel-gray  m  color  and  in  streak 
Its  luster  is  submetallic  Its  hardness  is  6-6  5  and  density  47  It  is 
infusible  before  the  blowpipe  With  fluxes  it  gives  the  usual  reactions 
for  manganese  It  is  soluble  in  HC1  yielding  chlorine 

It  occurs  in  veins  with  manganese  and  other  ores  in  Piedmont,  Italy, 
and  at  Pajsberg  and  various  other  places  m  Sweden,  where  its  origin 
is  secondary 

Hausmannite  (MngMnO^  crystallizes  like  braumte,  but  a :  <:= 
i  :  1 1573  and  its  crystals  are,  therefore,  distinctly  tetragonal  m  habit 
They  are  usually  simply  P(ni)  or  combinations  of  P(m)  and  fP(ii3), 
though  much  more  complicated  crystals  are  known  The  angle 
niAi7i=6o°  i'  Twins  and  fourlmgs  (Fig  102)  are  common,  with 

FIG    102 —Hausmannite.    (A)  Simple  Crystal,  P,  in  (p)  and  oP,  ooi  (c)      (B) 
Fivelmg  Twinned  about  P  oo  (101) 

P  oo  (101)  the  twinning  plane  The  cleavage  is  imperfect  parallel  to 
oP(ooi)  The  mineral  also  occurs  in  granular  masses. 

Hausmannite  is  brownish  black  Its  streak  is  chestnut  brown 
Its  hardness  is  5-5  5  and  density  4  8.  Its  reactions  are  the  same  as 
those  of  braumte 

Hausmannite  occurs  as  crystals  at  Ilmenau,  Thurmgia,  Ilfdd, 
Harz,  and  as  granular  masses  in  dolomite  at  Nordmark  and  several 
other  points  in  Sweden  Like  braumte  it  is  probably  a  decomposition 
product  of  other  manganese  minerals 



THE  nitrates  are  salts  of  nitric  acid  Only  two  are  of  importance 
to  us,  saltpeter  (KNOa)  and  chile  saltpeter  (NaNOs)  Both  are  color- 
less, or  white,  crystalline  bodies,  both  are  soluble  m  water  and  both  pro- 
duce a  cooling  taste  when  applied  to  the  tongue  The  potassium  com- 
pound is  distinguished  from  the  sodium  compound  by  the  flame  test 
Both  minerals  when  heated  in  the  closed  tube  with  KHSOi  yield  red 
vapors  of  nitrogen  peroxide  (NCfe) 

Soda  Niter  (NaNO3) 

Soda  niter,  or  chile  saltpeter,  is  usually  m  incrustations  on  mineral 
surfaces  or  m  massi\  e  forms  It  consists  of  63  5  per  cent  N2Os  and 
36  5  per  cent  Na20 

Its  crystals  are  in  the  ditrigonal  scalenohedral  class  of  the  hexagonal 
system  with  an  axial  ratio  of  a  :  c=i  :  8297.  They  are  usually  rhom- 
bohedrous  R(ioTi)  m  some  cases  modified  by  oR(oooi).  Apparently 
the  mineral  is  completely  isomorphous  with  calcite  (CaCOs) 

Its  cleavage  is  perfect  parallel  to  the  rhombohedron.  Its  hardness 
is  under  2,  its  density  about  2.27  and  its  melting  point  about  312°. 
Its  luster  is  vitreous,  color  white,  or  brown,  gray  or  yellow.  The  min- 
eral is  transparent  Its  refractive  indices  for  yellow  light  are:  w  =  1.5854, 


Soda  niter  deflagrates  when  heated  on  charcoal  and  colors  the  flame 
yellow.  When  exposed  to  the  air  it  attracts  moisture  and  finally  lique- 
fies. It  is  completely  soluble  in  three  times  its  own  weight  of  water. 

Occurrence  and  Localities  — The  principal  occurrences  of  the  mineral 
are  in  the  district  of  Tarapaca,  northern  Chile,  where,  mixed 
with  the  lodate  and  other  salts  of  sodium  and  potassium,  under  the 
name  caliche,  it  comprises  beds  several  feet  thick  on  the  surface  of  rain- 
less pampas,  and  in  Bolivia  at  Arane  under  the  same  conditions.  It  is 
associated  with  gypsum,  salt  and  other  soluble  minerals.  Smaller 



deposits  are  found  in  Humboldt  Co  ,  Nevada,  m  San  Bernardino  Co , 
Cal ,  and  in  southern  New  Mexico 

The  material  is  thought  to  result  from  the  action  of  microorganisms 
upon  organic  matter  decomposing  in  the  presence  of  abundant  air 

Uses  —Soda  niter  is  used  in  the  production  of  nitric  acid,  and  in  the 
manufacture  of  fertilizers  and  gunpowder  About  480,000  tons  are 
imported  into  the  United  States  annually  at  a  cost  of  $15,430,000 
Most  of  it  comes  from  Chile 

Since  soda  niter  usually  contains  sodium  lodate  as  an  impurity,  the 
mineral  is  an  important  source  of  iodine. 

Niter  (KNO3) 

Niter,  or  saltpeter,  resembles  soda  niter  in  appearance  It  gener- 
ally occurs  in  crusts,  in  silky  tufts  and  in  groups  of  acicular  crystals 
Its  crystals  are  orthorhombic  with  a  b  :  c=  5910  *  i  7011  Their 
habit  is  hexagonal  The  principal  forms  observed  on  them  are  oo  P(i  10), 
oo  P  00(100^,  oo  P  06(010),  oP(ooi),  P(in),  and  a  series  of  brachy- 
domes  In  many  respects  the  mineral  is  apparently  isomorphous  with 
aragonite  which  is  the  orthorhombic  dimorph  of  calcite  At  126°  it 
passes  over  into  an  hexagonal  (trigonal)  form  Its  cleavage  is  perfect 
parallel  to  Poo  (on)  Its  fracture  is  uneven,  its  hardness  2  and  den- 
sity 2  i  Its  medium  refractive  index  for  yellow  light,  /3=i  5056 

Niter  deflagrates  more  violently  than  soda  niter  and  detonates  with 
combustible  substances  It  fuses  at  aboat  335°  It  colors  the  blowpipe 
flaine  violet  It  is  soluble  in  water 

Occurrence  and  Localities — The  mineral  forms  abundantly  in  dry 
soils  in  Spain,  Egypt,  Persia,  Ceylon  and  India,  where  it  is  produced 
by  a  ferment,  and  on  the  bottoms  of  caves  m  the  limestones  of  Madison 
Co  ,  Ky ,  of  Tennessee,  of  the  valley  of  Virginia  and  of  the  Mississippi 

Production  — Most  of  the  niter  used  in  the  arts  is  manufactured,  but 
some  is  obtained  from  the  deposits  m  Ceylon  and  m  India  The 
amount  imported  in  1912  aggregated  6,976,000  Ib  ,  valued  at  $226,851 


The  borates  are  salts  of  bone  acid,  HsBOs,  metaboric  acid,  HBQz, 
tetrabonc  acid,  EfeBiOr,  hexabonc  acid,  EUBoOn,  and  various  poly- 
boric  acids  in  which  boron  is  present  in  still  larger  proportion  The 
metaacid  is  obtained  from  the  orthoacid  by  heating  at  100°,  at  which 


temperature  the  former  loses  one  molecule  of  water,  thus.  H3BO3  — 
H2O=HBO2,  and  the  tetraacid  by  heating  the  ^ame  compound  to  160" 
at  which  temperature  5  molecules  of  \\ater  are  lost  from  4  molecules  ot 
the  acid,  thus  4H3B03-5H2O=H2B407  Hexabonc  acid  may  be 
regarded  as  the  orthoacid  less  i|  molecules  of  water,  thus. 

Only  three  of  the  borates  are  important  enough  to  be  discussed 
here  These  are  borax,  a  sodium  tetraborate  (NaoB^Or  ioH<zO),  cole- 
manite,  a  hexaborate  (CasBoOn  slfeO)  and  boracite,  a  magnesium 
chloro-polyborate  (Mg5(MgCl)2Bi6Q3o)-  Borax  and  colemamte  are 
commercial  substances  that  are  produced  in  large  quantities 

All  borates  and  many  other  compounds  containing  boron  when 
pulverized  and  moistened  with  HoSO4  impart  an  intense  yellow-green 
color  to  the  flame  If  boron  compounds  are  dissolved  in  hydrochloric 
acid,  the  solution  will  turn  turmeric  paper  reddish  brown  after  drying 
at  100°  The  color  changes  to  black  when  the  stain  is  treated  with 

Borax  (H"a2B4O7  roH2O) 

Borax  occurs  as  crystals  and  as  a  crystalline  cement  between  sand 
grains  around  salt  lakes,  as  an  incrustation  on  the  surfaces  of  marshes 
and  on  the  sands  in  desert  regions,  and  dissolved 
in  the  water  of  certain  lakes  in  deserts.  It 
occurs  also  as  bedded  deposits  mterlayered  with 
sedimentary  rocks 

The  composition  of  borax  is  16  2  per  cent 
Na20,  36  6  per  cent  B2Qs  and  47  2  per  cent  H^. 

Crystals  are  monoclmic  (prismatic  class),  with 
a  :  b  :  c=i  0995  :  J  :  -5^29»  and  0=73°  25'  FlG  I03  —Borax  Crystal 
They  are  prismatic  in  habit  and  in  general  form  with  «  P,  no  (m), 
resemble  very  closely  crystals  of  pyroxene.  «P5o,iQo  (<*),<»?&, 
The  principal  planes  occurring  on  them  are  °IO_(6)'  °^I°°I  !f)' 
co  P  55  (100),  oo  P(no),  oP(ooi),  -P(in)  and  Jj  IZI  (a)  "*  2p'  221 
-2P(22i)  (Fig.  103).  Their  cleavage  is  perfect 
parallel  to  ooP  60(100),  and  their  fracture  concfaoidal.  The  angle 

The  mineral  has  a  white,  grayish  or  bluish  color  and  a  white  streak. 
It  is  brittle,  vitreous,  resinous  or  earthy;  is  translucent  or  opaque;  has 
a  hardness  of  2-2.5,  a  density  of  1.69-1.72,  and  a  sweetish  alkaline  taste. 
On  exposure  to  the  air  the  mineral  loses  water  and  tends  to  become  white 


and  opaque,  whatever  its  color  in  the  fresh  condition     Its  medium 
refractive  index  for  yellow  light,  0=  i  4686 

Before  the  blowpipe  borax  puffs  up  and  fuses  to  a  transparent 
globule  Fused  with  fluonte  and  potassium  bisulphate  it  colors 
the  flame  green  It  is  soluble  in  water,  yielding  a  weakly  alkaline 

Occurrence  —The  principal  method  of  occurrence  of  the  mineral  is 
as  a  deposit  from  salt  lakes  in  and  regions,  and  as  incrustations  on  the 
surfaces  of  alkaline  marshes  overlying  buried  borax  deposits  The 
original  beds  were  deposited  by  the  evaporation  to  dryness  of  ancient 
salt  lakes,  and  the  incrustations  were  produced  by  the  solution  of  these 
deposits  by  ground  water,  and  the  nse  of  the  solutions  to  the  surface  by 

Localities.— Borax  occurs  in  the  water  of  salt  lakes  in  Tibet,  of 
several  small  lakes  in  Lake  County,  and  of  Borax  Lake  in  San  Bernardino 
County  in  California,  and  in  the  mud  and  marshes  around  their  borders 
It  occurs  also  in  the  sands  of  Death  Valley  in  the  same  State,  and  in 
various  marshes  in  Esmeralda  County,  Nevada  Other  large  deposits 
are  found  in  Chile  and  Peru 

Uses  — Borax  is  used  as  an  antiseptic,  in  medicine,  in  the  arts  for 
soldering  brass  and  welding  metals,  and  in  the  manufacture  of  cosmetics 
Bone  acid  obtained  from  borax  and  colemamte  is  employed  in  the 
manufacture  of  colored  glazes,  in  making  enamels  and  glass,  as  an 
antiseptic  and  a  preservative  Some  of  the  borates  are  used  as  pig- 

Production — Borax  was  formerly  obtained  in  the  United  States, 
especially  in  California,  Oregon  and  Nevada,  by  the  evaporation  of 
the  water  of  borax  lakes,  by  washing  the  crystals  from  the  mud  on  their 
bottoms  and  by  the  leaching  of  the  mineral  from  marsh  soil  At  pres- 
ent, however,  nearly  all  the  borax  of  commerce  is  manufactured  from 

Colemanite  (Ca2B6On  sH2O) 

Colemamte  occurs  in  crystals  and  in  granular  and  compact  masses 
It  is  the  source  of  all  the  borax  now  manufactured  in  the  United  States. 

The  formula  ascribed  to  the  mineral  corresponds  to  27  2  per  cent 
CaO,  50.9  per  cent  6203  and  21  9  per  cent  H20.  As  usually  found, 
however,  it  contains  a  httle  MgO  and  SiCfe.  A  crystal  from  Death 
Valley,  California,  yielded: 

6203=5070;  0*0=27.31,  MgO=  10, 




The  mineral  crystallizes  in  the  monoclmic  system  (prismatic  class), 
m  short,  prismatic  crystals  (Fig  104),  with  the  axial  constants  a:b:c 
=  7769 .  i  :  5416  and  0=69°  43',  The  crystals  are  usualh  rich  in 
forms  Their  cleavage  is  perfect  parallel  to  ocOScloio),  and  less 
perfect  parallel  to  oP(ooi)  Their  fracture  is  uneven  The  angle 
no  A  110=72°  4' 

Colemanite  is  colorless,  milky  white,  yellowish  white  or  gray  It 
is  transparent  or  translucent,  has  a  vitreous  or  adamantine  luster,  a 
hardness  of  4  to  4  5  and  a  specific 
gravity  of  2  4  Its  index  of  refrac- 
tion for  yellow  light,  18=1.5920 

Before  the  blowpipe  it  decrep- 
itates, exfoliates,  and  partially 
fuses,  at  the  same  time  coloring 
the  flame  yellowish  green.  It  is 
soluble  in  hot  HC1,  but  from  the 
solution  upon  cooling  a  volumi- 
nous mass  of  boric  acid  separates 
as  a  white  gelatinous  precipitate 

It  is  easily  distinguished  from 
other  white  translucent  minerals, 
except  those  containing  boron, 
by  the  flame  test  It  is  distin- 
guished from  borax  by  its  insolu- 
bility in  water  and  from  boracite  by  its  inferior  hardness  and  crystal- 

Syntheses — Colemanite  has  been  prepared  by  treating  ulexite 
(NaCaBsOe  8H20)  with  a  saturated  solution  of  NaCl  at  70°. 

Occurrence  and  Origin — The  mineral  occurs  as  indefinite  layers 
interstratified  with  shale  and  limestones  that  are  associated  with  basalt 
The  rocks  contain  layers  and  nodules  of  colemanite  Gypsum  is  often 
associated  with  the  borate  and  m  some  places  is  in  excess.  The  cole- 
manite is  believed  to  be  the  result  of  the  action  of  emanations  from 
the  basalt  upon  the  limestone. 

Localities — Colemanite  occurs  in  Death  Valley,  California,  near 
Daggett,  San  Bernardino  County,  and  near  Lang  Station,  Los  Angeles 
County,  and  at  other  points  in  the  same  State,  and  in  western  Nevada, 
near  Death  Valley  A  snow-white,  chalky  variety  (priceite)  has  been 
found  hi  Curry  County,  Oregon,  and  a  compact  nodular  variety  (pander- 
mite)  at  the  Sea  of  Marmora,  and  at  various  points  in  Asia  Minor. 

Preparation  — Colemanite  is  at  the  present  time  the  principal  source 

FIG  104— Colemanite  Crystals  with  =cP 
no(m),  3?  5,  301  (v),  =*P5c,  100  (a), 
*  P» ,  oro  (b);  oP,  ooi  fc),  -P,  in 
(£),  2P*  02M«),  P3b,ouOO,  «pa, 
210  U),  aPoo,  201  (A),  2P,  221  (u)  and 
P,  In  00 


of  borax  The  crude  material  as  mined  contains  from  5  per  cent  to  35 
per  cent  of  anhydrous  boric  acid  (6203)  This  is  crushed  and  roasted 
The  colemamte  breaks  into  a  white  powder  vhich  is  separated  from 
pieces  of  rock  and  other  impurities  by  screening,  and  then  is  bagged  and 
shipped  to  the  refineries  where  it  is  manufactured  into  borax  and  boracic 

Production  — The  principal  mines  producing  the  mineral  in  1912 
were  situated  in  the  Death  Valley  section  of  Inyo  County,  near  Lang 
Station  in  Los  Angeles  County,  California,  and  in  Ventura  County  in 
the  same  State  The  total  production  during  the  year  was  42,315 
tons  of  crude  ore,  valued  at  $1,127,813  The  imports  of  crude  ore, 
refined  borax  and  boric  acid  during  the  same  year  were  valued  at  $i  1,200 
The  production  of  the  United  States  m  boron  acid  compounds  is 
about  half  that  of  the  entire  world,  with  Chile  producing  nearly  all 
the  rest 

Boracite  (Mg5(MgCl)2Bi6O3o) 

Boracite  is  interesting  as  a  mineral,  the  form  and  internal  structure 
of  which  do  not  correspond,  that  is,  do  not  possess  the  same  symmetry 
Its  crystals  have  the  well  marked  hextetrahedral  symmetry  of  the  iso- 
metric system,  but  their  internal  structure,  as  revealed  by  their  optical 
properties  is  orthorhombic  This  is  due  to  the  fact  that  the  substance 
is  dimorphous  Above  265°  it  is  isometric  and  below  that  temperature 
orthorhombic  Crystals  formed  at  temperatures  above  265°  assume 
the  isometnc  shapes.  As  the  temperature  falls  the  substance  changes 
to  its  orthorhombic  form,  and  there  results  a  pseudomorph  of  ortho- 
rhombic  boracite  after  its  isometric  dimorph 

It  is  a  salt  of  the  acid  which  may  be  regarded  as  related  to  boric 
acid  as  follows.  SHsBOs— 9H20=H6BsOi5.  Ten  atoms  of  hydrogen 
in  two  molecules  of  the  acid  are  replaced  by  Mgs  and  the  other  two  by 
a(MgCl).  The  resulting  combination  is  31  4  per  cent  MgO,  7  9  per 
cent  Cl  and  625  per  cent  BgC^ioi  8(0-Cl=i  9)  The  mineral 
alters  slowly,  taking  up  water,  so  that  some  specimens  yield  water  on 
analysis  and  in  the  dosed  tube  (stassfurti  e  and  parasite). 

The  forms  usually  found  on  the  crystals  are  -(in),   ooO(no), 

ooOoo(icx>),--(iIi)  (Fig.  105).    Usually  the  positive  and  negative 

tetrahedrons  may  be  distinguished  by  their  luster,  the  faces  of  the  posi- 
tive form  being  brilliant  and  those  of  the  negative  form  dull.  The 
crystals  are  isolated,  or  embedded,  and  rarely  in  groups  They  are 


strongly  pyroelectnc  with  the  analogue  pole  in  the  negative  tetrahedrons. 
The  mineral  is  also  found  massive 

Boracite  is  transparent  or  translucent  and  is  gra\ ,  yellow,  or  green 
Its  streak  is  white  Its  luster  is  vitreous  Its  cleavage  is  indistinct 
parallel  to  0(m)  and  its  fracture  is  conchoidal  ^  n  ^ 
The  mineral  is  brittle  Its  hardness  is  7  and 
its  density  3  Its  refractive  index  £,  for  yellow 
light,  =  i  667 

Boracite  fuses  easily  before  the  blowpipe 
with  intumescence  to  a  white  pearly  mass,  at 
the  same  time  colonng  the  flame  green  With 

copper  oxides  it  colors  the  flame  azure-blue  FIG  105  —Boracite 
When  moistened  with  Co(NOs)2  it  gives  the  Cr>stal  with  =cO=c, 
pink  reaction  for  magnesium  Some  massive  «»/iz;,  «O,  no  id), 
forms  yield  water  in  the  closed  tube,  in  conse-  -\ — ,  m  (0)  and  —  ~f 
quence  of  weathering  The  mineral  is  soluble  _  ,  , 
inHCl  ll 

Boracite  is  distinguished  from  other  boron  salts  by  its  crystallization, 
its  lack  of  cleavage  and  its  much  greater  hardness  The  massive  vari- 
eties which  resemble  fine-grained  white  marble  can  be  distinguished 
from  this  by  the  flame  coloration,  hardness  and  reaction  with  HC1 

Syntheses. — Crystals  have  been  formed  by  heating  borax,  MgCfe 
and  a  little  water  at  275°,  and  by  fusing  borax  with  a  mixture  of  NaCl 
and  MgCk 

Occurrence. — Boracite  occurs  in  beds  with  anhydrite,  gypsum  and 
saltj  and  as  crystals  in  metamorphosed  limestones 

Localities — It  is  found  as  crystals  in  gypsum  and  anhydrite  at 
Luneburg,  Hanover,  and  Segeberg,  Holstein,  in  carnallite  at  Stassfurt, 
Prussia,  and  in  radiating  nodules  (stassfurtite)  and  in  massive  layers 
associated  with  salt  beds  at  the  last-named  locality  It  is  rare  in  the 
United  States 

Uses  and  Prodwhon  —Boraute  is  utilized  in  Europe  as  a  source  of 
boron  compounds.  Turkey  produces  annually  about  12,000  tons, 


THE  carbonates  constitute  an  important,  though  not  a  very  large, 
group  of  minerals,  though  one  of  them,  calcite,  is  among  the  most  com- 
mon of  all  minerals  They  are  all  salts  of  carbonic  acid  (EkCOs)  Those 
in  which  all  the  hydrogen  has  been  replaced  by  metal  are  normal  salts, 
those  in  which  the  replacement  has  been  by  a  metal  and  a  hydroxyl 
group  are  basic  salts  Both  groups  are  represented  by  common  minerals 

The  normal  salts  include  both  anhydrous  salts  and  salts  combined 
with  water  of  crystallization  Illustrations  of  the  three  classes  of  car- 
bonates are-  CaCOs,  calcite,  normal  salt,  Na2COs  loEfeO,  soda, 
hydrous  salt  and  (Cu  OH^COs,  malachite,  basic  salt  All  carbonates 
effervesce  in  hot  acids  The  basic  salts  yield  water  at  a  high  tempera- 
ture only,  the  hydrous  ones  at  a  low  temperature 

The  carbonates  are  all  transparent  or  translucent,  and  all  are  poor 
conductors  of  electricity,  Most  of  them  are  practically  nonconductors 


The  anhydrous  normal  carbonates  comprise  the  most  important 
carbonates  that  occur  as  minerals  Most  of  them  are  included  in  a 
single  large  group  whose  members  are  dimorphous,  crystallizing  in  the 
ditrigonal  scalenohedral  class  of  the  hexagonal  system  and  in  the  holo- 
hedral  division  (rhombic  bipyramidal  class)  of  the  orthorhombic  sys- 
tem. The  calcium  carbonate  exists  in  three  forms  but  only  two  are 
known  to  occur  as  minerals 


The  relation  of  the  dimorphs  of  this  group  to  one  another  has  been 
subjected  to  much  study,  especially  with  reference  to  the  two  forms  of 
CaCQs-  The  orthorhombic  form,  aragonrie,  passes  into  the  hexagonal 
form,  calcite,  upon  heating  to  about  400°.  At  all  temperatures  below 
970°,  calcite  is  the  stable  form  Moreover,  while  calcite  crystallizes 
from  a  dilute  Solution  of.CaCQa  in  water  containing  002  at  a  low  tem- 



perature,  aragomte  separates  at  a  temperature  approaching  that  of 
boiling  water— the  more  freely,  the  less  C02  in  the  solution  Arag- 
omte crystals  will  also  separate  from  a  solution  of  calcium  carbonate, 
if,  at  the  same  time,  it  contains  a  gram  of  an  orthorhombic  carbonate, 
or  a  small  quantity  of  a  soluble  sulphate  Some  of  the  other  carbon- 
ates, for  instance,  strontiamte  (the  orthorhombic  SrCCfe),  pass  over 
into  an  hexagonal  form  like  that  of  calcite  at  700°,  but  again  change 
to  the  orthorhombic  form  upon  cooling  For  convenience  the  group 
is  divided  for  discussion  into  the  calcite  division  and  the  aragomte 


The  calcite  division  of  carbonates  includes  nine  or  more  distinct 
compounds  and  a  number  of  well  defined  \aneties  of  these  Six  of  the 
compounds  are  common  minerals  Afl  crystallize  in  the  ditngonal 
scalenohedral  class  of  the  hexagonal  system  and  are  thus  isomorphous 
Their  most  common  crystals  have  a  rhombohedral  habit.  The  names  of 
the  six  common  members  with  their  axial  ratios  are: 

Calcite  CaCOs  a    c=i  :  8543 

Magnesite  MgCOs  =1  :  8095 

Siderite  FeCOs  =i  :  8191 

Khodochrosite  MnCOs  =i  •  .8259 

Smit\somte  ZnCOs  =i  :  8062 

There  is  usually  also  included  in  the  group  the  mineral  dolomite,  which 
is  a  calcium  magnesium  carbonate  in  which  CaCOs  and  MgCOs  are 
present  in  the  molecular  proportions,  thus  MgCOs  CaCOs,  or 
MgCa(COs)2  Its  crystals  are  similar  to  those  of  calcite  and  its  physical 
properties  are  intermediate  between  those  of  calate  and  magnesite 
Its  symmetry,  however,  as  revealed  by  etching  is  tetartohedral  (rhom- 
bohedral class). 

The  close  relationship  existing  between  the  members  of  the  group 
(including  dolomite)  will  be  appreciated  upon  comparing  the  data  in 

the  following  table 

Ref  Indices 




a  :  c 


tt                     € 


•  3 










Dolomite     . 

-  3 




























































Calcite  (CaCO3) 

Calcite  is  one  of  the  most  beautifully  crystallized  minerals  known 
Its  crystals  are  very  common,  and  sometimes  very  large  They  are 
usually  colorless,  though  sometimes  colored,  and  are  nearly  always 
transparent  Besides  occurring  in  crystals  the  mineral  is  often  found 
massive,  in  granular  aggregates,  in  stalactites,  in  pulverulent  masses, 

FIG  106 

FIG  108 

FEG.  107  FIG  109 

FIG.  106. — Calcite  Crystal  with  — |R,  oiTa  (e)  and  «s  R,  joTo  (m)     Nail-head  Spar 

FIG,  107  —  Calcite  Crystal  with  m  and  e     Prismatic  Type 

FIG  108  — Calcite  Ciystals  with  m,  R»,  2131  (p)  and  R,  loli  (r)     Dog-tooth  Spar 
FIG  109  —Calcite  with  r,  v,  4R,  4041  (M)  and  R8,  3251  (y) 

in  radial  groupings,  in  fibrous  masses  and  in  a  variety  of  other  forms  As 
calate  is  soluble  in  water  containing  COa,  it  has  often  been  found  pseu- 
domorphing  other  minerals. 

Theoretically,  calcite  contains  56  per  cent  CaO  and  44  per  cent  COg, 
but  practically  the  mineral  contains  also  small  quantities  of  Mg,  Fe, 
Mn,  Zn  and  Pb,  metals  whose  carbonates  are  isomorphous  with 

Hie  forms  that  have  been  observed  on  calcite  crystals  are  arranged 



in  such  a  manner  as  to  produce  three  distinct  types  of  habit,  as  fol- 
lows (i)  the  rhombohedral  type,  bounded  by  the  flat  rhombohedrons, 
R(ioTi),  —  JR(oiT2)  and  often  blunt  scale- 
nohedrons,  like  R3(2i3i)  and  |R2(3i45) 
in  which  the  rhombohedrons  predominate 
(Fig  106),  (2)  the  pnsmatic  type,  with 
the  pnsm  oo  P(io7o)  predominating,  and 
—  £R(oil2)  as  the  principal  termination 
(Fig  107),  and  (3)  dog-tooth  spar,  contain- 
ing the  same  scalenohedrons  as  on  the  first 
type  mentioned  above  with  other  steeper 
ones  and  small  steep  rhombohedral  planes 
(Fig  108,  109,  no)  Nail-head  spar  con- 
tains the  flat  rhombohedron  —  |R(oil2) 
with  the  pnsm  oo  P(ioTo)  (Fig  106). 

Some  of  the  crystals  are  very  compli- 
cated, belonging  to  no  one  of  the  distinct 

types  descnbed  above,  but  forming  barrel-shaped  or  almost  round 
bodies     Over  300  well  established  forms  have  been  identified  on  them. 

Twins  are  common  The  principal  laws  are:  (i)  twinning  plane 
oP(oooi),  with  the  vertical  axis  common  to  the  twinned  parts  (Fig 
111),  (2)  twinning  plane  — fR(oiT2),  with  the  two  vertical  axes  inclined 

FIG  no— Pnsmatic  Crystals 
of  Calcite  Terminated  by 
Scalenohedrons  and  Rhom 
bohedrons    from  Cumber- 
land, England 

FIG   in. 

FIG  112 

FIG  in  — Calate,  R*  (2131)  Twinned  about  oP  (oooi) 
FIG  112  — Calcite    Twin  and  Polysynthetic  Trilling  of  R  (ion)  about  —  £R  (0112)- 

at  an  angle  of  about  52^°  (Fig.  112)  and  (3)  twinning  plane  R(ioTi), 
with  the  vertical  axes  inclined  89°  14'  (Fig.  113), 

Twins  of  the  second  dass  can  easily  be  produced  artificially  on  cleav- 
age rhombs  by  pressing  a  dull  knife  edge  on  the  obtuse  rhombohedral 
edge  with  sufficient  force  to  move  a  portion  of  the  mass  (Fig.  114). 
The  change  of  position  of  a  portion  of  the  calcite  does  not  destroy  its 



transparency  in  the  least     Repeated  twinning  of  this  kind  is  frequently 
seen  in  marble  (Fig  115),  ^vhere  it  gives  nse  to  parallel  lamellae 

The  cleavage  of  calcite  is  so  perfect  parallel  to  R  that  crystals  when 

FIG  113  *  FIG.  114 

FIG  113  — Calcite  with  m,  v  and  e,  Twinned  about  R  (loTi) 
FIG  114  — Artificial  Twin  of  Calcite,  with  —  JR  (oils)  the  Twinning  Plane. 

shattered  by  a  hammer  blow  usually  break  into  perfect  little  rhombo- 
hedrons  Its  hardness  is  about  3  and  its  density  2  713  Pure  calcite 
is  colorless  and  transparent,  but  most  specimens  are  white  or  some  pale 

shade  of  red,  green,  gray, 
blue,  yellow,  or  even  brown 
or  black  when  very  impure, 
and  are  translucent  or  opaque 
The  mineral  is  very  strongly 
doubly  refracting,  (see  p  213) 
It  is  a  very  poor  conductor  of 

The  principal  vaneties  of 
the  mineral  to  which  distinct 
names  have  been  given  are: 

Iceland  spar,  the  trans- 
parent variety  used  in  the 
manufacture  of  optical  instru- 

Satin  spar,  a  fine,  fibrous 
variety  with  a  satiny  luster 
Limestone,     granular    ag- 
occurnng   as    rock 

FIG  115  —Thin  Section  of  Marble  Viewed  by 
Polarized  Light.  The  dark  bars  are  poly- 
synthetic  twinning  lamellae  Magnified  5 


Marble,  a  crystalline  limestone,  showing  when  broken  the  cleavage 
faces  of  the  individual  crystals. 

Ltike&apkic  stone  a  very  fine  and  even-grained  limestone 


Stalactites,  cylinders  or  cones  of  calcite  that  hang  from  the  roofs  of 
caves  They  are  formed  by  the  evaporation  of  dripping  T\ater 

Stalagmites,  corresponding  cones  on  the  floors  of  caves  beneath  the 

Mexican  onyx,  banded  crystalline  calcite,  often  transparent. 
Usually  portions  of  stalactites 

Travertine,  a  deposit  of  white  or  yellow  porous  calcite  produced 
in  springs  or  rivers,  often  around  organic  material  like  the  blades 
or  roots  of  grass. 

Chalk,  a  fine-grained,  pulverulent  mass  of  calcite  occurring  in 
large  beds 

In  the  closed  tube  calcite  often  decrepitates  Before  the  blowpipe  it 
is  infusible  It  colors  the  flame  reddish  yellow  and  after  heating  reacts 
alkaline  toward  moistened  litmus  paper  The  mineral  dissolves  with 
evolution  of  CO2  in  cold  hydrochloric  acid  Its  dissociation  tempera- 
ture l  is  898°,  though  it  begins  to  lose  C0>  at  a  much  lower  temperature 

The  reaction  with  HC1,  together  \vith  the  alkalinity  of  the  mineral 
after  heating,  its  softness  and  its  easy  cleavage,  distinguish  calcite  from 
all  other  minerals  In  massive  forms  it  has  been  thought  that  it  could 
be  distinguished  from  aragomte  by  heating  its  ponder  with  a  httle 
Co(NOs)2  solution  Aragomte  was  thought  to  become  violet-colored 
in  a  few  minutes  while  calcite  remained  unchanged,  but  recent  work 
proves  that  this  test  cannot  be  relied  upon 

Syntheses — Calcite  crystals  are  obtained  b\  allowing  a  solution 
of  CaCOs  in  dilute  carbonic  acid  to  evaporate  slowly  in  contact  with  the 
air  at  ordinary  temperatures  If  evaporated  at  from  80°  to  100° 
ordinary  temperatures,  or  in  the  presence  of  a  httle  sulphate,  the  ortho- 
rhombic  aragonite  will  form,  Calcite  is  also  formed  by  heating  arag- 
onite  to  400-470° 

Occurrence  and  Origin. — The  mineral  is  widely  distributed  in  beds, 
in  veins  and  as  loose  deposits  on  the  bottoms  of  springs,  lakes  and  nvers. 
Its  principal  methods  of  origin  are  precipitation  from  solutions,  the 
weathering  of  calcareous  minerals,  and  secretion  by  organisms. 

Calcite  is  the  most  important  of  all  pseudomorphmg  agencies.  It 
forms  pseudomorphs  after  many  different  minerals  and  the  hard  parts 
of  animals 

Localities.— The  most  noted  localities  of  .crystallized  calcite  are: 
Andreasberg  in  the  Harz;  Freiberg,  Schneeberg  and  other  places  in 
Saxony;  Kapnik,  in  Hungary,  Traversella,  in  Piedmont,  Alston  Moor 

1  The  dissociation  temperature  of  a  carbonate  is  that  temperature  at  which  the 
pressure  of  the  released  CO*  equals  one  atmosphere 


and  Egremont,  in  Cumberland,  Matlock,  in  Derbyshire,  and  the  mines 
of  Cornwall,  England,  Guanajuato,  Mexico,  Lockport,  N  Y  ,  Ke- 
weenaw  Point,  Mich  ,  the  zinc  regions  of  Illinois,  Wisconsin  and 
Missouri,  Nova  Scotia,  etc 

Iceland  spar  is  obtained  in  the  Eskefjord  and  the  Breitifjord  in 
Iceland  Travertine  is  deposited  from  the  waters  of  the  Mammoth 
Hot  Springs,  Yellowstone  National  Park  It  occurs  also  along  the 
River  Arno,  near  Tivoli,  Rome 

Uses. — Calcite  has  many  important  uses  In  the  form  of  Iceland 
spar,  on  account  of  its  strong  double  refraction,  it  is  employed  in  optical 
instruments  for  the  production  of  polarized  light  Calcite  rocks  are 
used  as  building  and  ornamental  stones  They  are  employed  also  as 
fluxes  in  smelting  operations,  as  one  of  the  ingredients  in  glass-making 
and  in  the  manufacture  of  lime,  cement,  whiting,  and  in  certain  printing 
operations.  Limestone  is  also  used  as  a  fertilizer 

Production  — The  calcite  rock  marketed  in  the  United  States  during 
1912  was  valued  at  about  $44,500,000  It  was  used  as  follows  In 
concrete,  $5,634,000,  in  road  and  railroad  making,  $12,000,000,  as  a 
flux,  $10,000,000,  as  building  and  monumental  stone,  $12,800000, 
in  sugar  factories,  $335,000,  as  riprap,  $1,183,000,  for  paving,  $279,000, 
and  for  other  uses,  $2,400,000  Moreover,  the  value  of  the  Portland 
cement  manufactured  during  the  year  amounted  to  $67,017,000,  the 
quantity  of  lime  made  to  $13,970,000,  the  value  of  the  hydrated 
lime  to  $1,830,000,  and  of  sand-lime  brick  to  $1,170,884  The  quantity 
of  limestone  required  for  these  manufactures  is  not  known,  but  it  was 
very  great. 

Magnesite  (MgCO3) 

Magnesite  usually  occurs  in  fine-grained  white  masses  Crystals 
are  rare  Pure  magnesite  consists  of  52  4  per  cent  CCb  and  47  6  per 
cent  MgO.  It  usually,  however,  contains  some  iron  carbonate 

Magnesite  is  completely  isomorphous  with  calcite     Its  cleavage  is 

perfect  parallel  to  R(ioTi).    Its  hardness  is  about  4  and  the  density  3  i. 

The  mineral  is  transparent  or  opaque.    It  varies  in  color  from  white 

to  brown,  but  always  has  a  white  streak     Its  dissociation  temperature 

•  o 

is  445  - 

Magnesite  behaves  like  calcite  before  the  blowpipe  It  effervesces 
in  hot  hydrochloric  acid  and  readily  yields  the  reaction  for  magnesia 
with  Co(NQs)2  It  is  most  easily  distinguished  from  the  latter  mineral 
by  its  density,  by  the  fact  that  it  does  not  color  the  blowpipe  flame  with 
the  yellowish  red  tint  of  calcium  and  does  not  effervesce  in  cold  HCL 


Synthesis  — Magnesite  crystals  may  be  obtained  by  heating  MgSO 
in  a  solution  of  XajCOa  at  160°  in  a  closed  tube 

Occurrence  and  Origin  — Magnesite  usualh  occurs  in  \  ems  and  masses 
associated  with  serpentine  and  other  magnesium  rocks  irom  which  it 
has  been  formed  by  decomposition  It  is  often  accompanied  by  brucite 
talc,  dolomite  and  other  magnesium  compounds  It  has  recently  been 
described  as  occurring  also  in  a  distinct  bed  near  Mohave,  CaL,  inter- 
stratified  with  cla>  s  and  shales  It  is  thought  that  in  this  case  it  ma} 
have  been  precipitated  fron*  solutions  of  magnesium  salts  by  Xa^COs 

Localities  — The  mineral  is  found  abundantly  m  many  foreign  local- 
ities and  at  Bolton,  Mass  ,  Bare  Hills,  near  Baltimore,  Md ,  and  in 
Tulare  Co.,  Cal ,  and  near  Texas,  Penn  The  largest  deposits  are  in 
Greece  and  Hungary 

Uses. — Magnesite  is  employed  very  largely  in  the  manufacture  of 
magnesite  bricks  used  for  lining  converters  in  steel  works,  in  the  lining 
of  kilns,  etc  ,  m  the  manufacture  of  paper  from  wood  pulp,  and  in  mak- 
ing artificial  marble,  tile,  etc  From  it  are  also  manufactured  epsom 
salts,  magnesia  (the  medicinal  preparation)  and  other  magnesium  com- 
pounds, and  the  carbon  dioxide  used  in  making  soda  water 

Production  — All  of  the  magnesite  mined  in  the  United  States  comes 
from  California,  where  the  yield  was  10,512  tons  in  1912,  valued  at 
$105,120.  Most  of  the  magnesite  used  in  the  United  States  is  imported 
from  Hungary  and  Greece  In  1912,  14,707  tons  of  crude  material 
entered  the  country  and  125,000  tons  of  the  calcined  product,  the  total 
value  of  which  ^as  $1,370,000 

Siderite  (FeCO3) 

Siderite  is  an  important  iron  ore,  though  not  as  much  used  as  formerly 
It  is  found  crystallized  and  massive,  in  botryoidal  and  globular  forms 
and  m  earthy  masses 

In  composition  the  mineral  is  FeCOa,  which  is  equivalent  to  62  i 
per  cent  FeO  (48  2  per  cent  Fe)  and  37  9  per  cent  COj-  Manganese, 
calcite  and  magnesium  are  also  often  present  in  it. 

Crystals  are  more  common  than  those  of  magnesite.  They  fre- 
quently contain  the  basal  plane  and  the  steep  rhombohedrons— 8R(o8Si) 
and  —  sRfesi).  R(ioli)  and  — |R(oiT2)  are  common  The  faces 
of  the  rhombohedron  are  frequently  curved.  Compare  (Fig  125.) 

The  cleavage  of  Siderite  is  like  that  of  the  other  minerals  of  this 
group.  Its  hardness  is  3  5-4  and  density  3  85.  In  color  the  mineral 
is  sometimes  white,  but  more  frequently  it  is  some  shade  of  yellow  or 
brown  Its  streak  is  white  Most  specimens  are  translucent. 


In  the  closed  tube  siderite  decrepitates,  blackens  and  becomes  mag- 
netic It  is  only  slcroly  affected  by  cold  acids  but  it  effervesces  briskly 
in  hot  ones 

Siderite  is  distinguished  from  the  other  carbonates  by  its  reaction 
for  iron 

The  mineral  changes  on  exposure  into  limonite  and  sometimes  into 
hematite  or  even  into  magnetite 

Synthesis  —  Crystals  of  sidente  may  be  obtained  by  heating  a  solu- 
tion of  FeSCU  with  an  excess  of  CaCOs  at  200° 

Occurrence  and  Origin  — The  mineral  is  often  found  accompanying 
metallic  ores  in  veins  It  occurs  also  as  nodules  in  certain  clays  and  in 
the  coal  measures.  In  some  cases  it  appears  to  be  a  direct  deposit  from 
solutions  In  others  it  is  a  result  of  metasomatism  and  m  others  is  an 
ordinary  weathering  product 

Localities  —The  crystallized  variety  is  found  at  Freiberg,  in  Saxony, 
at  Harzgerode,  in  the  Harz,  at  Alston  Moor,  and  in  Cornwall,  Eng- 
land, and  along  the  Alps,  in  Styna  and  Cannthia  Cleavage  masses 
are  present  in  the  cryolite  from  Greenland 

Workable  beds  of  the  ore  are  present  m  Columbia  Co  ,  and  at  Rossie, 
in  St.  Lawrence  Co ,  N  Y  ,  in  the  coal  regions  of  Pennsylvania  and 
Ohio,  and  in  clay  beds  along  the  Patapsco  River,  in  Maryland  The 
massive  or  nodular  ore  from  clay  banks  is  known  as  ironsto?  e  The 
impure  bedded  sidente  interstratified  with  the  coal  shales  is  known 
as  black-band  ore 

Production. — Only  10,346  tons  of  sidente  were  produced  in  the  United 
States  during  1912,  all  of  it  coming  from  the  bedded  deposits  in  Ohio 
This  was  valued  at  $20,000 

Rhodochrosite  (MnCO3) 

This  mineral  sometimes  occurs  in  distinct  crystals  of  a  rose-red 
color,  but  it  is  usually  found  in  cleavable  masses,  in  a  compact  form, 
or  as  a  granular  aggregate  Sometimes  it  is  m  incrustations  It  is 
not  of  commercial  importance  in  North  America 

Pure  manganese  carbonate  containing  61  7  per  cent  MnO  and  38  3 
per  cent  CQs  is  rare  The  mineral  is  usually  impure  through  the  addi- 
tion of  the  carbonates  of  iron,  calcium,  magnesium  or  zinc 

The  most  prominent  forms  on  crystals  of  rhodochrosite  are  R(ioYi), 
— |R(oil2),  ooP2(ii2o),  oR(oooi)  and  various  scalenohedrons 

Its  cleavage  is  perfect  parallel  to  R  The  mineral  is  brittle  Its 
hardness  is  about  4  and  its  density  about  3.55  Its  luster  is  vitreous, 
and  its  color  red,  brown,  or  yellowish  gray.  Its  streak  is  white  When 


heated  it  begins  to  lose  CCb  at  about  320":  but  its  dissociation  temper- 
ature is  632° 

The  mineral  is  infusible,  but  T\hen  heated  before  the  blowpipe  it 
decrepitates  and  changes  color  When  treated  in  the  borax  bead  it 
gives  the  violet  color  of  manganese,  and  \\hen  fused  with  soda  on  char- 
coal it  yields  a  bluish  green  manganate  It  dissoh  es  in  hot  hydro- 
chloric acid 

There  are  but  fe\v  minerals  resembling  pure  rhodochrosite  m  appear- 
ance From  all  of  these,  except  the  silicate,  rhodonite  ip  3801,  it  is 
distinguished  by  its  reaction  for  manganese  It  is  distinguished  from 
rhodonite  by  its  hardness,  its  cleavage  and  its  effervescence  with  acids 
The  impure  varieties  are  very  like  some  forms  of  siderite,  from  which, 
of  course,  the  manganese  test  will  distinguish  it. 

Synthesis — Small  rhombohedrons  of  rhodochrosite  have  been  pro- 
duced by  heating  a  solution  of  MnSQ*  with  an  excess  of  CaCCfe  at  200° 
in  a  closed  tube 

Occurrence  and  Origin  — Rhodochrosite  occurs  in  veins  associated 
with  ores  of  silver,  lead,  copper  and  other  manganese  ores  and  in  bedded 
deposits  It  is  the  result  of  hydrothermal  or  contact  metamorphism, 
and  of  weathering  of  other  manganese-bearing  minerals 

Localities. — The  mineral  is  found  at  Schemmtz,  in  Hungary,  at 
Nagyag,  in  Transylvania,  at  Glendree,  County  Clare,  Ireland,  where  it 
forms  a  bed  beneath  a  bog,  at  Washington,  Conn ,  in  a  pulverulent 
form,  at  Franklin,  N  J  ,  at  the  John  Reed  Mine,  Ahconte,  Lake  Co  , 
and  at  Rico,  Colo  ,  at  Butte  City,  Mont  ,  at  Austin,  Xev.,  and  on 
Placentia  Bay,  Newfoundland  The  Colorado  and  Montana  specimens 
are  well  crystallized 

Uses  —The  mineral  is  mined  with  other  ores  of  manganese.  Occa- 
sionally it  is  employed  as  a  gem  stone. 

Smithsonite  fZnCO3) 

Smithsomte,  or  "dry-bone  ore,"  is  rarely  well  crystallized.  It 
appears  as  druses,  botryoidal  and  stalactitic  masses,  as  granular  aggre- 
gates and  as  a  fnable  earth. 

In  ZnCOs  there  are  64  8  per  cent  ZnO  and  35  2  per  cent  CCte  Smith- 
somte usually  contains  iron  and  manganese  carbonates,  often  small 
quantities  of  calcium  and  magnesium  carbonates  and  sometimes  traces 
of  cadmium  A  specimen  from  Marion,  Arkansas,  gave: 

ZnO       CdO   FeO     CaO      CuO      CCfe     CdS      Sift>  Total 

64  12      .63      .14      .38       tr.       34-68       25         06  100  26 


The  mineral  is  closely  isomorphous  with  calcite,  R(ioTi),  —  iR(oiT2), 
4R(404i),  ooR2(ii2o),  oR(oooi)  and  R3(2i3i)  being  present  on  many 
crystals  The  R  faces  are  rough  or  curved 

Its  cleavage  is  parallel  to  R(ioli).  Its  hardness  is  5  and  its  density 
about  4  4.  The  luster  of  the  mineral  is  vitreous,  its  streak  is  white  and 
its  color  white,  gray,  green  or  brown  It  is  usually  translucent,  occa- 
sionally transparent  When  heated  to  300°  for  one  hour  it  loses  all  of 
its  C02 

When  heated  in  the  closed  tube  CC>2  is  driven  off,  leaving  ZnO  as  a 
yellow  residue  while  hot,  changing  to  white  on  cooling  The  mineral 
is  infusible  before  the  blowpipe  If  a  small  fragment  be  moistened  with 
cobalt  nitrate  solution  and  heated  in  the  oxidizing  flame  it  becomes 
green  on  cooling  When  heated  on  charcoal  a  dense  white  vapor  is 
produced.  This  forms  a  yellow  coating  on  the  coal,  which,  when  it 
cools,  turns  white  If  this  be  moistened  with  cobalt  nitrate  and  reheated 
in  the  oxidizing  flame  it  is  colored  green. 

The  above  reactions  for  zinc,  together  with  the  effervescence  of  the 
mineral  in  hot  hydrochloric  acid  distinguish  smithsomte  from  all  other 

Smithsomte  forms  pseudomorphs  after  sphalerite  and  calcite  and  is 
pseudomorphed  by  quartz,  hmomte,  calamine  and  goethite 

Synthesis  — Microscopic  crystals  of  smithsomte  may  be  produced  by 
precipitating  a  zinc  sulphate  solution  with  potassium  bicarbonate  and 
allowing  the  mixture  to  stand  for  some  time. 

Occurrence. — Smithsomte  occurs  in  beds  and  veins  in  limestones, 
where  it  is  associated  with  galena  and  sphalente  and  usually  with  cala- 
mine (p  396)  It  is  especially  common  in  the  upper,  oxidized  zone  of 
veins  of  zinc  ores  and  as  a  residual  deposit  covering  the  surface  of  weath- 
ered limestone  containing  zinc  minerals 

Localities— The  mineral  is  found  at  Nerchinsk,  Siberia,  Bleiberg, 
in  Cannthia;  Altenberg,  Aachen,  Province  of  Santander,  Spain,  at 
Alston  Moor  and  other  places  in  England,  at  Donegal,  in  Ireland,  at 
Lancaster,  Penn  ,  at  Dubuque,  Iowa,  in  Lawrence  and  Marion  Coun- 
ties, Arkansas;  and  in  the  lead  districts  of  Wisconsin  and  Missouri  (see 
galena  and  sphalerite). 

The  Wisconsin  and  Missouri  localities  are  the  most  important  ones 
in  North  America.  Here  the  ore  occurs  in  botryoidal,  in  stalactitic 
and  in  earthy,  compact,  cavernous  masses  of  a  dull  yellow  color  incrusted 
with  druses  of  smithsonite  crystals,  of  calamine  and  of  other  minerals, 
principally  of  lead  This  is  the  variety  known  as  "  dry  bone  " 

Uses  — The  mineral  was  formerly  an  important  ore  of  zinc,  being 


mined  alone  for  smelting  It  is  no\v  mined  only  in  connection  with 
calamine  and  other  zinc  ores,  and  all  are  worked  up  together.  A  trans- 
lucent green  or  greenish  blue  variety  occurring  at  Laurium,  Greece, 
and  at  Kelly,  New  Mexico,  is  sometimes  employed  for  ornamental  pur- 
poses. About  $650  worth  of  the  material  from  New  Mexico  was  utilized 
as  gem  material  in  1912 


This  division  of  the  carbonates  includes  the  orthorhombic  (rhombic 
bipyramidal)  dimorphs  of  the  members  of  the  calcite  group  which, 
together,  form  a  well  characterized  isodimorphous  group.  The  carbon- 
ate of  calcium  is  found  well  crystallized  in  both  dmsions,  but  the  other 
carbonates  are  common  to  one  only  They  actually  occur  in  both  divi- 
sions, but  they  are  found  as  .common  members  of  one  and  only  as 
isomorphous  mixtures  with  other  more  common  forms  in  the  other 
Thus,  barium  carbonate  is  a  common  orthorhombic  mineral  under  the 
name  of  uithente  It  occurs  also  with  CaCOs  in  mixed  crystals  under 
the  name  bancalcite,  or  neotype,  \*hich  is  hexagonal.  (See  also  p.  212 
and  p  213  ) 

The  common  members  of  the  aragonite  division  are: 

Aragomte  CaCOs  Sp  Gr.  =  2  936  a  :  b  :  c=  6228  :  i 

Stronfaamte  SrCOs  =3  706  ==  6090 :  i 

Witkente  BaCOa  =4  325  =  5949  :  i 

Cerussite  PbCOs  ac6  574  =  6102 :  i      7232 

Aragonite  (CaCOs) 

Aragomte  occurs  m  a  great  variety  of  forms.  Sometimes  it  is  in 
distinct  crystals,  but  more  frequently  it  is  in  oolitic  globular  and  reni- 
form  masses,  in  divergent  bundles  of  fibers  or  of  needle-like  forms,  in 
stalactites  and  in  crusts. 

In  composition  aragonite  is  like  calcite.  It  often  contains  small 
quantities  of  the  carbonates  of  strontium,  lead  or  zinc. 

Crystals*are  often  acicular  with  steep  domes  predominating.  Some 
of  the  simplest  crystals  consist  of  oop(uo),  ooP  00(010),  fP  00(032), 
Poo  (on),  4?(44i),  9P(9Qi)  and  ooP2(i2o)  (Fig.  116).  Twinning  is 
common.  The  twinning  plane  is  often  ooP(iio).  By  repetition  this 
gives  nse  to  pseudohexagonal  forms,  resembling  an  hexagonal  prism  and 
the  basal  plane  (see  Figs  117  and  118),  The  angle  no  A  i  "10=63°  48'. 

The  cleavage  of  aragonite  is  distinct  parallel  to  oo  p  06  (oio)  and 
indistinct  parallel  to  oo  P(no).  Its  hardness  is  3.5-4  and  density  about 
2  93  Its  luster  is  vitreous  and  its  color  white,  often  tiiigcd  with  gray, 




green  or  some  other  light  shade     Its  streak  is  white  and  the  mineral  is 
transparent  or  translucent    Its  indices  of  refraction  for  yellow  light  are 
a=SI  j^oo,  7=1  6857     At  400°  it  passes  over  into  calcite 

Before  the  blowpipe  aragomte  whitens  and  falls  to  pieces     Other- 
wise its  reactions  are  like  those  of  caktte,  from  which  it  can  be  distin- 


'"  ui 

FIG  116 

FIG  117 

FIG  116  — Aragomte  Crystal  with  °o  P,  no  (m),    oo  P  So ,  oio  (6)  and  P  So ,  on 
FIG  117  — Aragomtc  Twin  and  Trilling  Twinned  about  co  P  (no) 


FIG  1 18— Trilling  of  Aragomte  Twinned  about  <*>P  (no)  (A)  Cross-section 
(B)  Resulting  pseudohexagonal  group,  resembling  an  hexagonal  prism  and 
basal  plane 

guished  by  its  crystallization,  its  lack  of  rhombohedral  cleavage  and  its 

Synthesis  —Solutions  of  CaCOs  in  dilute  HaCOs  form  crystals  of 
aragomte  when  evaporated  at  a  temperature  of  about  90°  In  general, 
hot  solutions  of  the  carbonate  deposit  aragomte,  while  cold  solutions 
deposit  calcite  If  the  solution  contains  some  sulphate  or  traces  of 
strontium  or  lead  carbonates,  mixed  crystals  consisting  principally  of 
the  aragomte  molecule  are  formed  at  ordinary  temperature, 

Occurrence  and  Origin — Aragomte  occurs  in  beds,  usually  with 
gypsurn.  It  is  also  deposited  from  hot  waters  and  from  coid  waters 


containing  a  sulphate  (as  from  sea  water)  The  pearly  layer  of  oyster 
shells  and  the  body  of  the  shells  of  some  other  mollusca  are  composed 
of  calcium  carbonate  crystallizing  like  aragomte  Aragomte  is  often 
changed  by  paramorphism  into  calcite,  pseudomorphs  of  which  after 
the  former  mineral  are  quite  common 

Localities — The  mineral  is  found  at  Aragon,  Spain,  at  Bilm,  in 
Bohemia,  in  Sicily,  at  Alston  Moor,  England,  and  at  a  number  of 
other  places  in  Europe  It  occurs  in  groupings  of  interlacing  slender 
columns  (fios  /em),  m  the  iron  mines  of  Styria  Stalactites  are  abundant 
at  Leadhills,  Lanarkshire,  Scotland,  and  a  silky  fibrous  variety  known  as 
satmspar,  at  Dayton,  England 

In  the  United  States  crystallized  aragomte  occurs  at  Mine-la-Motte, 
Mo  ,  and  in  the  lands  of  the  Creek  Nation,  Oklahoma  Flos  fern  has 
been  reported  from  the  Organ  Mts ,  New  Mexico,  and  fibrous  masses 
from  Hoboken,  N  J  ,  Lockport,  Edenville  and  other  towns  in  New  York 
and  from  Warsaw,  111 

Strontianite  (SrCO3) 

In  general  appearance  and  in  its  manner  of  occurrence  strontianite 
resembles  aragomte  Its  crystals  are  often  acicular  in  habit  though 
repeated  twins  are  common  The  angle  no  A  iTo=62°  41' 

The  composition  of  pure  strontianite  is  SrO=7o  i,  C02=2g  9,  but 
the  mineral  usually  contains  an  admixture  of  the  barium  and  calcium 

Strontianite  is  brittle,  its  hardness  is  3  5-4  and  its  density  3  7 

Before  the  blowpipe  strontianite  swells  and  colors  the  flame  with  a 
crimson  tinge  It  dissolves  in  hydrochloric  acid  The  solution  im- 
parts a  crimson  color  to  the  blowpipe  flame  When  treated  with  sul- 
phuric acid  it  yields  a  precipitate  of  SrSO*  Its  refractive  indices  for 
yellow  light  are  a=  i  5199,  7=1  668  Its  dissociation  temperature  is 


Aragomte,  witherite  (BaCOs)  and  strontianite  are  so  similar  in  ap- 
pearance and  in  general  properties  that  they  can  be  distinguished  from 
one  another  best  by  their  chemical  characteristics  They  are  all  sol- 
uble in  hydrochloric  acid  and  these  solutions  impart  distinctive  colors 
to  the  blowpipe  flame  (see  p  477) 

Syntheses — Crystals  of  strontianite  are  obtained  by  precipitating 
a  hot  solution  of  a  strontium  salt  by  ammonium  carbonate,  and  by  cool- 
ing a  solution  of  SrCOs  in  a  molten  mixture  of  NaCl  and  KC1 

Occurrence, — Strontianite  occurs  in  veins  in  limestone  and  as  an 


alteration  product  of  the  sulphate  (celestite)  where  this  is  exposed  to  the 
weather  It  is  probably  in  all  cases  a  deposit  from  water 

Localities — Strontiamte  is  the  most  common  of  all  strontian  com- 
pounds It  frequently  occurs  as  the  filling  of  metallic  veins  It  forms 
finely  developed  crystals  at  the  Wilhelmme  Mine  near  Munstei,  West- 
phalia At  Schohane,  N  Y ,  it  occurs  as  crystals  and  as  gianular  masses 
in  nests  in  limestone  It  is  found  also  at  other  places  in  New  York,  in 
Mifflm  Co  ,  Penn  ,  and  on  Mt  Bannell  near  Austin,  Texas. 

Uses—  Strontium  compounds  are  little  used  m  the  arts  The 
hydroxide  is  employed  to  some  extent  m  refining  beet  sugar  and  the 
nitrate  m  the  manufacture  of  "  red  fire  "  Othei  compounds  aie  used 
m  medicine  All  the  strontium  salts  used  in  the  United  States  arc 

Witherite  (BaC03) 

Withente  differs  very  little  in  appearance  or  in  manner  of  occurrence 
from  aragomte  Its  crystals  are  nearly  always  m  repeated  twins  that 

have  the  habit  of  hexagonal  pyramids  (Fig. 
119)     The  angle  noAiTo«62°  46', 

When  pure  the  mineral  contains  77  7  pei 
cent  BaO  and  22  3  per  cent  C02 

It  is  much  heavier  than  the  calcium  car- 
bonate, its  density  being  43     Its  hardness 
FIG  119— wuhcriic  Twinned    is  3  to  4     Its  refractive  mdc\  foi  yellow 
about  COP  (no),  thus Im.-    llght    /s==I740     ils  (hbboaation  tenii mu- 
tating Hexagonal  Combina-    ture  Jg          0 

It  dissolves  readily  in  dilute  hydrochloric 

acid  with  effervescence,  and  from  thib  solution,  even  when  dilute,  sul- 
phuric acid  precipitates  a  heavy  white  precipitate  of  BaSO-t,  winch, 
when  heated  m  the  blowpipe  flame,  imparts  to  it  a  yellowish  green 

Witherite  is  distinguished  from  the  other  carbonates  by  its  crys- 
tallization, and  the  color  it  imparts  to  the  blowpipe  flame. 

Syntheses  —Crystals  are  produced  by  precipitating  a  hot  solution  of 
a  barium  salt  with  ammonium  carbonate,  and  by  cooling  a  molten 
xnagma  composed  of  NaCl  and  BaCO? 

Locahfoes  — Witherite  is  not  a  very  common  mineral  in  the  United 
States,  but  it  occurs  in  large  quantity  associated  with  lead  minerals  in 
veins  at  Alston  Moor,  in  Cumberland  and  near  Hexham,  in  Northum- 
berland, England  Some  of  the  crystals  found  in  these  places  measure 
as  much  as  six  inches  in  length 



Its  best  known  locality  in  the  United  States  is  Lexington,  Kentucky, 
where  the  mineral  is  associated  with  the  sulphate,  bante 

Uses  — It  is  used  to  some  extent  as  a  source  of  banum  compounds 
The  importations  of  the  mineral  during  1912  aggregate  $25,715 

Cerussite  (PbC03) 

Cerussite  generally  occurs  in  crystals  and  in  granular,  earthy  and 
fibrous  masses  of  a  white  coloi 

The  pure  lead  carbonate  contains  C02=i6  5  and  PbO=835j  but 
the  mineral  usually  contains  in  addition  some  ZnCOa 

FIG  1 20 

FIG  121 

FIG  122 

FIG  120  —  Cerussite  Crystal  with  cop  no  (w),  ooPoo  ,  100  (0),  ooPoo,  oio  (6), 
P,  in  (p),  oo  P^,  130  (r),  2Poo,  021  (i),  Pw,on  (fc),  JPoo,  012  (x)  and 
oP,  ooi  (c) 

FIG  121  —  Cerussite  Tnlhng  Twinned  about  *>  P(no) 

FIG  122  —  Cerussite  Tnllmg  Twinned  about  «o 

Its  simple  crystals  are  tabular  combinations  of  oo  P(i  10)  ,  oo  P  08  (oio) 
oo  Poo  (100)  and  various  brachydomes  (Fig  120),  and  these  are  often 
twinned  in  such  a  way  as  to  produce  six  rayed  stars  (Fig  121),  or  other 
symmetrical  forms  (Fig  122)  Groups  of  interpenetrating  crystals 
are  also  common  The  angle  iioAiio=620  46'. 

The  color  of  the  mineral  is  usually  white,  but  its  surface  is  frequently 
discolored  by  dark  decomposition  products  Its  luster  is  adamantine 
or  vitreous  and  its  hardness  is  3-3  5  Its  density  =6.5  Its  refractive 
indices  for  yellow  light  are  a  =  i  8037,  £  =  2  0763,  7=2  0780 

The  mineral  is  dissolved  by  nitric  acid  with  effervescence  and  by 
potassium  hydroxide  Before  the  blowpipe  it  decrepitates,  turns  yellow 
and  changes  to  lead  oxide  On  charcoal  it  is  reduced  to  a  metallic 
globule,  and  yields  a  white  and  yellow  coating 


Cerussite  is  not  easily  confused  with  other  minerals  It  is  well  char- 
acterized by  its  high  specific  gravity,  its  reaction  for  lead,  and  is  dis- 
tinguished from  the  sulphate  (anglesite)  by  effervescence  with  hot  acids 

Syntheses  —Crystals  have  been  obtained  by  heating  lead  formate  with 
water  in  a  closed  tube,  and  by  treatment  of  a  lead  salt  by  a  solution  of 
ammonium  carbonate  at  a  temperature  of  iso°-i8o° 

Occurrence  and  Origin  — The  mineral  occurs  at  all  localities  at  which 
other  lead  compounds  are  found,  since  it  is  often  produced  from  thes* 

FIG  123 — Radiate  Groups  of  Cerussite  on  Galena  from  Park  City  Distrid,  Utah. 
(After  J  M  BoHlwell) 

latter  by  the  action  of  the  atmosphere  and  atmospheric  water  It  is, 
therefore,  usually  found  m  the  upper  portions  of  veins 

Locates  —Cerussite  crystals  of  great  beauty  are  found  m  many  of 
the  lead-producing  districts  of  Europe  and  also  at  Phoemxville,  Penn  ; 
near  Union  Bridge,  m  Maryland,  at  Austin's  Mines,  Wythe  Co.,  Vir- 
ginia, and  occasionally  in  the  lead  mines  of  Wisconsin  and  Missouri, 
In  the  West  it  occurs  at  Leadville,  Colo  ,  at  the  Flagstaff  and  other 
mines  m  Utah  (Fig  123),  and  at  several  different  mines  in  Arizona. 

Uses, — It  is  mined  with  other  lead  compounds  as  an  ore  of  the  metal 


Dolomite  (MgCa(CO3)2) 

Dolomite  is  apparently  isomorphous  with  calcite  but  the  etch 
figures  on  rhombohedral  -faces  prove  it  to  belong  m  the  trigonal 
rhombohedral  class  It  occurs  as  crystals  and  in  all  the  forms  charac- 
teristic of  calcite  except  the  fibrous 

Nearly  all  calcite  contains  more  or  less  magnesium  carbonate,  but 
most  of  the  mixtures  are  isomorphous  with  calcite  and  magnesite 
When  the  ratio  between  the  two  carbonates  reaches  5435  per  cent 
CaCOs  45  65  per  cent  MgCOs,  which  is  equal  to  the  ratio  between 
the  molecular  weights  of  the  two  substances,  or  in  other  words  when  the 
two  carbonates  are  present  in  the  compound  in  the  ratio  of  one  molecule 
to  one  molecule,  the  mineral  is  called  dolomite  The  calculated  com- 
position of  dolomite  (MgCa(COs)2)  is  30  4  per  cent  CaO,  217  per  cent 
MgO  and  47  8  per  cent  CCte 

The  crystals  of  dolomite  are  usually  rhombohedral  combinations  of 
the  rhombohedron  R(ioli)  with  the  scalenohedron 
R3(2i3i)  (Fig  124),  and  its  tetartohedral  forms, 
and  often  the  prism  oop2(ii2o)  and  the  basal 
plane  Its  axial  ratio  is  a:c**im  8322  Twins 
are  not  rare,  with  oR(oooi)  and  R(ioTi)  the 
twinning  planes  The  R  planes  are  often  curved, 
frequently  with  concave  surfaces  (Fig  125)  The 

angle  loli  A7ioi  =  730.  ^  , 

rro.       i  i j  i      -j.  -£    i.  ni      FIG  124— Dolomite 

The  cleavage  of  dolomite  is  perfect  parallel        crystal  with  4R 

to   R     The   mineral  is  brittle     Its  hardness  is        40^T  y^  and  Op' 
3  5-4  and  density  2  915     Its  luster  is  vitreous  or        oooi  (c) 
pearly  and  its  color  white,  red,  green,  gray  or 
brown     Its  streak  is  always  white  and  the  mineral  is  translucent  or 
transparent     Its  refractive  indices  for  yellow  light  are     w=  16817, 
€=  i  5026     The  important  varieties  recognized  are 
Pearlspar,  with  curved  faces  having  a  pearly  luster 
Granular  or  saccharoidd,  including  many  marbles  and  magne'San 

Dolomifoc  limestone,  including  much  hydraulic  limestone 
Many  dolomites  are  intermixed  with  the  carbonates  of  iron,  manga- 
nese, cobalt  or  zinc  and  these  are  known  as  ferriferous  dolomite,  etc 

Dolomite  behaves  like  calcite  before  the  blowpipe  and  in  the  closed 
tube  It,  however,  dissolves  only  slowly,  if  at  all,  m  cold  hydrochloric 
acid,  except  when  very  finely  powdered,  though  dissolving  readily  with 
effervescence  in  hot  acid 


The  reaction  toward  cold  acid  and  its  greater  hardness  easily  dis- 
tinguish dolomite  from  calcite  It  is  distinguished  from  magnetite  by 
the  flame  reaction 

Occurrence  and  Origin  —Dolomite,  like  the  calcium  carbonate,  occurs 
crystallized  m  veins,  and  as  granular  masses  forming  gicat  beds  of  rock 
It  is  a  precipitate  from  solutions  and  a  metasomatic  alteration  product 
of  calcite 

Localities  — Its  crystals  are  present  at  many  places,  among  them 
Bex,  in  Switzerland,  Traversella,  in  Piedmont,  Guanajuato,  in  Mexico, 
Roxbury,  in  Vermont,  Hoboken,  N  J.,  Niagara  Palls,  the  Quarantine 

FIG  125. — Group  of  Dolomite  Crystals  from  Jophn,  Mo     Flat  Rhombohedrons  with 

Curved  Faces 

Station,  and  Putnam,  N.  Y  ,  Joplin,  Mo  ,  and  Stony  Pouil,  N  C.    It 
is  also  very  widely  spread  as  beds  of  dolomitic  limestone 

Uses  — Dolomite  is  used  for  many  of  the  purposes  served  by  calcite, 
indeed,  much  of  the  material  used  as  marble,  limestone,  etc  ,  contains  a 
large  percentage  of  magnesium  carbonate  It  is  not,  however,  used  as  a 
flux  or  m  the  manufacture  of  Portland  cement,  nor  as  a  source  of  lime 

Ankerite  (Ca(Mg  Fe)  (003)2)  is  a  ferruginous  dolomite.  It  is  an 
isomorphous  mixture  of  the  carbonates  of  calcium,  magnesium  and  iron, 
in  which  the  FeCOa  replaces  a  part  of  the  MgCOs  in  dolomite  It  is 
usually  in  rhombohedral  crystals,  with  the  angle  xoTi  A 1101-73°  48' 
Its  color  is  white,  gray  or  red  and  its  streak  is  white  Its  hardness 
=3  5-4,  and  its  density = 2  98  It  also  occurs  m  coarse  and  fine-grained 
granular  masses,  Ankente  is  infusible  before  the  blowpipe.  In  the 


closed  tube  it  darkens  and  when  heated  on  charcoal  it  becomes  mag- 
netic It  occurs  in  veins,  especially  those  containing  iron  minerals 
It  has  been  found  at  Antwerp  and  other  places  m  northern  New  York. 


Carbonates  of  the  general  composition  CaBa(COs)2  occur  (i)  as  a 
series  of  mixed  crystals  isomorphous  with  caicite  under  the  name  hart- 
calctte,  (2)  as  a  series  of  mixed  crystals  isomorphous  with  aragomte 
known  as  alstomte  or  bromhte,  and  (3)  a  typical  double  salt,  barytocalctte, 
which  is  monoclmic  Both  alstomte  and  barytocaicite  occur  in  veins 
of  lead  ores  and  of  bante 

Barytocaicite,  CaBa(COs)2  is  monoclmic  (prismatic  class),  with 
a  :  b  .  c~  7717  i  6255  and  £=73°  52'  It  forms  crystals  bounded 
by  oo  P  66  (100),  ccP(no),  oP(ooi),  and  a  series  of  clmopyramids,  of 
which  2P2  (12!)  and  sP$  (i  5!)  are  common  It  also  occurs  massive  Its 
perfect  cleavage  is  parallel  to  ooP(no)  The  mineral  is  white,  gray, 
greenish  or  yellowish  Its  streak  is  white,  hardness  =4  and  sp  gr  = 
3  665  It  is  transparent  or  translucent  Before  the  blowpipe  frag- 
ments fuse  on  thin  edges,  and  assume  a  pale  green  color,  due  to  the 
presence  of  a  little  manganese  The  mineral  is  soluble  in  HC1  Its 
principal  occurrence  is  Alston  Moor,  Cumberland,  England. 


The  basic  carbonates  are  salts  in  which  all  or  a  portion  of  the  hydro- 
gen of  carbonic  acid  is  replaced  by  the  hydroxides  of  metals  There 
are  only  three  minerals  belonging  to  the  group  that  need  be  referred  to 
here  Two  are  copper  compounds  One  is  the  bright  green  malachite 
and  the  other  the  blue  azunte  The  composition  of  the  former  may  be 


represented  by  the  formula  ;>C03,  and  that  of  the  latter  by 



Cu==(COs)2.  Both  are  used  to  some  extent  as  ores  of  the  metal, 

though  their  value  for  this  purpose  is  not  great  at  the  present  time 
They  may  easily  be  distinguished  from  all  other  minerals  by  their 
distinctive  colors,  by  the  fact  that  they  yield  water  in  the  closed  tube 
and  by  their  effervescence  with  acids  The  third  mineral  (hydrozincite) 
is  a  white  substance  that  occurs  as  earthy  or  fibrous  incrustations  on  other 
zinc  compounds.  Its  composition  corresponds  to  2ZnCOs  sZn(OH)2 


Its  hardness  =  2-2  5  and  its  specific  gravity  is  about  3  7     Only  the  two 
copper  compounds  are  described  m  detail 

Malachite  ((CuOH)2CO3) 

Malachite  usually  occurs  in  fibrous,  radiate,  stalactitic,  granular 
or  earthy,  green  masses,  or  as  small  drusy  crystals  covering  other  copper 
compounds  The  mineral  contains,  when  pure,  19  9  per  cent  CO2, 
71  9  per  cent  CuO  and  8  2  per  cent  KbO 

Well  defined  crystals  are  usually  very  small  monoclmic  prisms  (mon- 
oclmic  prismatic  class),  with  an  a\ial  ratio  8809  •  i 
•  4012  and  #=6i°  50'  Their  predominant  forms 
are  ooPoo(ioo),  ooPo>(oio),  ooP(no),  and 
oP(ooi)  Contact  twins  arc  common,  with 
oo  P  60(100)  the  twinning  plane  (Fig  126)  The 
angle  no  A  iTo=  75°  40' 

The  puie  mineral  is  bright  green  in  color  and  has 
a  light  green  stieak  It  possesses  a  vitieous  luster, 
FIG  126 -Malachite  but  this  becomes  silky  m  fibrous  marc*  and  dull 
Crystal  with  «?,  m  massive  specimens  Crystals  are  translucent 
no  (w),  ooPw,  and  massive  pieces  aic  opaque.  Translucent 
ioo  (a),  and  oP,  pieces  are  pleochroic  in  yellowish  green  and  dark 
cot  (c)  Twinned  green  tmts  Thc  clcavage  1S  perfcct  paidud  to 

oP(ooi)  Thc  haidness  of  malachite  is  3  5-4,  and 
its  density  about  3  9  Its  refractive  index,  /3,  for  yellow  light  ==i  88 

Malachite  turns  black  and  fuses  befoic  the  blowpipe  and  tinges  the 
flame  green  With  NaaCOs  on  charcoal  it  yields  a  copper  globule.  It  is 
difficultly  soluble  m  pure  water,  but  is  easily  dissolved  m  water  con- 
taining C02  It  is  soluble  with  effervescence  in  HCl  and  its  solution 
becomes  deep  blue  on  the  addition  of  an  excess  of  ammonia.  When 
heated  in  a  closed  glass  tube,  it  gives  an  abundance  of  water.  Boiled 
with  water  it  turns  black  and  loses  its  COa 

Malachite,  on  account  of  its  characteristic  color,  may  be  easily  dis- 
tinguished from  all  other  minerals  but  some  varieties  of  turquoise  and 
a  few  copper  compounds,  such  as  atacamite  (p  144)  It  may  be  dis- 
tinguished from  all  of  these  by  its  effervescence  with  acids 

Synthesis. — Malachite  crystals  have  been  obtained  with  the  form  of 
natural  crystals  by  heating  a  solution  of  copper  carbonate  m  ammonium 

Occurrence  and  Origin — Malachite  is  a  frequent  decomposition 
product  of  other  copper  minerals,  being  formed  rapidly  in  moist  places. 


It  occurs  abundantly  in  the  upper  oxidized  portions  of  veins  of  copper 
ore,  where  it  is  associated  with  azurite,  cuprite,  copper,  kmomte  and  the 
sulphides  of  iron  and  copper,  often  pseudomorphmg  the  copper  minerals 
The  green  stain  noticed  on  exposed  copper  trimmings  of  buildings  is 
composed  in  part  of  this  substance 

Localities — The  mineral  occurs  in  all  copper  mines  At  Chessy, 
France,  it  forms  handsome  pseudomorphs  after  cuprite  In  the  United 
States  it  has  been  found  in  good  specimens  at  Cornwall,  Lebanon  Co , 
Penn  ,  at  Mineral  Point,  Wisconsin,  at  the  Copper  Queen  Mine,  Bisbee, 
and  at  the  Humming  Bird  Mine,  Morenci,  Arizona,  and  in  the  Tintic 
district,  Utah. 

Uses  —In  addition  to  its  use  as  an  ore  of  copper  the  radial  and  mass- 
ive forms  of  malachite  are  employed  as  ornamental  stones  for  inside 
decoration  The  massive  forms  are  also  sawn  into  slabs  and  polished 
for  use  as  table  tops  and  are  turned  into  vases,  etc 

Production  — As  malachite  is  mined  with  other  copper  compounds, 
the  quantity  utilized  as  an  ore  of  the  metal  is  not  known  The  amount 
produced  in  the  United  States  during  1912  for  ornamental  purposes  was 
valued  at  $1,085  This,  however,  included  also  a  mixture  of  malachite 
and  azurite. 

Azurite  (Cu(CuOH)2(CO3)3) 

Azurite  is  more  often  found  in  crystals"  than  is  malachite.  It  occurs 
also  as  veins  and  incrustations  and  in  massive,  radiated,  and  earthy 

FIG  127— Azurite  Crystals  with  oP,  oot  (c),    -Pco,  101  (<r),    ooPoo,  100  (a), 
P,  YII  (*),  oo  P,  no  (»),  -2P,  221  (A),  jPa,  243  (d)  and  P  &  ,  on  (/) 

forms  associated  with  malachite  and  other  copper  compounds.    Its 
most  frequent  associate  is  malachite,  into  which  it  readily  alters 

In  composition  azurite  is  25  6  per  cent  CCh,  69  2  per  cent  CuO,  and 
5  2  per  cent  EfeO  It  changes  rapidly  to  malachite,  and  sometimes  is 
reduced  to  copper 

The  crystals  are  tabular,  prismatic,  or  wedge-shaped  monochmc 
forms  (monochmc  prismatic  dass),  with  an  axial  ratio  a  .  b  :  c=  8501  : 
i  :  r  7611,  and  P~Bj°  36',    They  are  usually  highly  modified,  58  or 


more  different  planes  having  been  identified  on  them  The  predominant 
ones  are  oP(ooi),  —  POO(IOI),  ooP(no),  -2P(22i)  and  oopoo(ioo). 
(Fig  127  )  The  angle  no  A  1*0=80°  40' 

The  mineral  is  dark  blue,  vitreous,  and  translucent  or  transparent, 
and  is  pleochroic  in  shades  of  blue  It  is  brittle  Its  streak  is  light 
blue,  its  hardness  3  5-4  and  density  3  8  Its  cleavage  is  distinct  parallel 
to  Poo  (on) 

The  blowpipe  and  chemical  reactions  for  azunte  are  the  same  as 
those  for  malachite  By  them  the  mineral  is  easily  distinguished  from 
the  few  other  blue  minerals  known 

Synthesis  —  Crystals  have  been  formed  on  calcile  by  allowing  frag- 
ments of  this  mineral  to  lie  in  a  solution  of  CuNOj  for  a  year  or  more 

Occurrence  —  The  mineral  occurs  in  the  oxidized  zone  of  copper  veins. 
It  is  an  intermediate  product  m  the  change  of  other  coppei  compounds 
to  malachite 

Localities  —  Azunte  occurs  m  beautiful  crystals  at  Cressy,  France, 
near  Redruth,  in  Cornwall,  at  Phoenix  ville,  Pcnn  ,  at  Mineral  Point, 
Wis  ,  at  the  Copper  Queen  Mine,  Bisbce,  Aiu  ,  at  the  Mammoth 
Mine,  Tintic  district,  Utah,  at  Hughes's  Mine,  California,  and  at  many 
other  copper  mines  in  this  country  and  abroad 

From  Morenci,  Ariz  ,  Mr  Kunz  describes  specimens  consisting  of 
spherical  masses  composed  of  alternating  layers  of  malachite  and 
azunte,  which,  when  cut  across,  yield  surfaces  banded  by  alternations  of 
bright  and  dark  blue  colors 

Uses  —  Azurite  is  mined  with  other  copper  minerals  as  an  ore  of  cop- 
per It  is  also  used  to  a  slight  extent  as  an  ornamental  stone  (see  mal- 


The  hydrous  carbonates  are  salts  containing  water  of  crystalliza- 
tion They  are  carbonates  of  sodium  or  of  this  metal  with  calcium  or 
magnesium  Some  of  them  occur  in  abundance  in  the  waters  of  salt  or 
bitter  lakes,  but  very  few  are  known  to  occur  m  any  large  quantity  in 
solid  form  Among  the  commonest  are: 

Soda  or  natron  Na2COa  xoBfeO  monochmc 

Trona  HNas  (C0s)2  -  aEfeO  monoclmic 

Gayliissite  NagCa(C03)2  sEfeO  monoclimc 

Hydromagnestie  Mg^OH^COaVsBfeO  orthorhombic 

These  minerals  occur  either  m  the  muds  of  lakes  or  as  crusts  upon  the 
mud  or  upon  other  minerals, 


Natron  occurs  only  in  solution  and  in  the  dry  mud  on  the  borders 
of  lakes 

Trona,  or  urao,  (HNa3(C03)2  2H20)  is  found  as  crystals  in  the 
mud  of  Borax  Lake,  California,  as  a  massive  bed  in  Churchill  Co., 
Nevada,  and  as  thin  coatings  on  rocks  in  other 
places.  Its  crystallization  is  monochnic  (pns-  ^  c 
matic  class),  with  the  axial  ratio,  2  8426 :  i  .  V  7 

29494  and  18=76°  31'     Its  crystals  are  usually      \ *     -> 

bounded  by  oP(ooi),  ooP  66(100),  -P(m)  and  FIG  128— Trona  Ciys- 
+P(Tn)  (Fig  128)  Fibrous  and  massive  forms  tal  with  oP,  ooi  (c), 
are  common  The  mineral  has  a  perfect  cleavage  °° p  *  >  I0°  (fl)  and 
paraUel  to  oo  P  60  (100)  It  is  gray  or  yellowish  +P' m  (o) 
and  has  a  colorless  streak  It  has  a  vitreous  luster,  a  hardness  of 
2  5-3,  and  a  density  of  2  14  It  is  soluble  in  water  and  has  an  alkaline 
taste  It  exhibits  the  usual  reactions  for  Na  and  for  carbonates 

Gaylussite  (Na2Ca(COs)2  5H20)  also  occurs  as  crystals  in  the 
muds  of  certain  lakes,  especially  Soda  Lake,  near  Ragtown,  Nevada, 
and  Menda  Lake,  Venezuela,  and  in  clays  under  swamps  in  Railroad 
Valley,  in  Nevada  Its  crystals  are  monochnic 
(prismatic  class)  with  a  :  b  :  c=i  4897  :  i :  1 4442 
and  0=78°  27'  They  are  usually  bounded  by 
oo  P(no),  P  oo  (on),  and  ^P(Ti2)  (Fig  129),  or  by 
these  planes  and  oP(ooi)  and  oo  P  66  (100).  They 
are  either  prismatic  because  of  the  predominance 
of  Pob(oii)  and  oP(ooi),  or  are  octahedral  m 
habit  because  of  the  nearly  equal  development  of 
P  ob  (on)  and  oo  P(iio).  Their  cleavage  is  perfect 
FIG  1 29 -Gaylussite  para]iel  to  ooP(no) 

Crystal  with  oop,          ^  ^^  .g  ^^  ^       Uowish  and  trans^ 

no  (m),  Poo ,011  J 

(e)and  JP,Ti2  (r).    lucent      Its  hardness  is  2-3   and  density  199 

It  is  very  brittle     When  heated  m  the  closed 

tube  it  decrepitates  and  becomes  opaque     It  loses  its  water  at  100° 

In  the  flame  it  melts  easily  to  a  white  enamel  and  colors  the  flame  yellow 

It  is  partially  soluble  in  water,  leaving  a  white  powdery  residue  of  CaCOs 

and  is  entirely  soluble  in  acids  with  effervescence     The  mineral  occurs 

in  such  large  quantity  in  the  clays  underlying  swamps  in  Railroad  Valley, 

Nevada,  that  its  use  has  been  suggested  as  a  source  of  NagCOs- 


THE  sulphates  are  salts  of  sulphuric  acid  A  large  number  are 
known  to  occur  in  nature  but  many  of  them  are  dissolved  in  the  waters 
of  salt  lakes  Of  the  remaining  ones  only  a  few  are  very  common 
These  may  be  divided  into  an  anhydrous  normal  group,  a  basic  group  and 
a  hydrated  group  In  addition,  there  are  several  minerals  that  are 
sulphates  mixed  with  chlorides  or  carbonates 

All  the  sulphates  that  are  soluble  in  water  give  the  test  for  sulphuric 
acid  When  heated  with  soda  on  charcoal  they  are  reduced  to  sulphides 
The  mass  when  placed  on  a  silver  com  and  moistened  with  a  drop  of 
water  or  of  hydrochloric  acid  partly  dissolves  and  stains  the  silver  dark 
brown  or  black 

The  sulphates  when  pure  are  all  white  and  transparent,  and  are  all 
nonconductors  of  electricity 


The  anhydrous  normal  sulphates  ha\c  the  general  formula  R/2S04 
or  R"S04  The  most  common  ones  are  sulphates  of  the  alkaline  earths 
and  lead  They  belong  in  a  single  group  which  is  orthorhombic  The 
few  less  common  ones  are  sulphates  of  the  alkalies  or  of  the  alkalies 
and  alkaline  earths  Only  two  of  the  latter  are  described* 

Glauberite  (Na2Ca(SO4)2) 

Glaubente  may  be  regarded  as  a  double  salt  of  the  composition 
NaaS04  CaSO/t,  which  requires  511  per  cent  Na2S04  and  48.9  per  cent 
CaS04  The  mineral  contains  22  3  per  cent  Na20,  20  i  per  cent  CaO 
and  57  6  per  cent  SOs 

It  nearly  always  occurs  in  monochmc  crystals  (prismatic  class), 
with  an  axial  ratio  i  2209  .  i  i  0270  and  #=67°  49'.  The  most  fre- 
quent combination  is  oP(ooi),  — P(ni),  ooP(no),  ooP  06(100), 
3P3(3iT)  and  +P(u7),  with  oP(ooi)  prominent  (Fig  130)  The 
cleavage  is  perfect  parallel  to  oP(ooi)  The  angle  noAiTos=96°  58'. 




Glaubente  is  yellow,  gray  or  brick-red  m  color,  is  transparent  or 
translucent  and  has  a  white  streak,  a  vitreous  luster  and  a  conchoidal 
fracture  Its  hardness  is  2  5-3  and  its  specific 
gravity  about  28  It  is  brittle  It  is  partly 
soluble  m  water,  imparting  to  the  solution  a 
slight  saltiness  The  red  color  of  many  speci- 
mens is  due  to  the  presence  of  inclusions 

Before  the  blowpipe  the  mineral  decrepi- 
tates, whitens   and   fuses  easily  to  a  white 
enamel,  at  the  same  time  coloring  the  flame  FIG  130— Glaubente  Crys- 
yellow     It  is  soluble  m  HC1  and  in  a  large     talwithoP.ooi  («),  <*p, 
quantity  of  water     In  a  small  quantity  of 
water  it  is  partially  dissolved  with  loss   of 
transparency  and  the  production  of  a  deposit  of 

It  sometimes  alters  to  calcite 

Occurrence—  Glaubente  is  associated  with  rock  salt  and  other  de- 
posits from  bodies  of  salt  water  It  is  found 
at  Villa  Rubia,  m  Spam,  and  elsewhere 
in  Europe,  and  m  the  Rio  Verde  Valley, 
Arizona  and  at  Borax  Lake,  California 

no  (m),  oo  P  oo ,  100  (a) 
and  — P,  in  (s) 

FIG  131  — Thenarditc  Crystal 
with  oo  P,  no  (w),  P,  nT 
(o),  IPS,  106  (0  and  oP, 
ooi  (c) 

Thenardite  (Na2S04)  occurs  as  ortho- 
rhombic  crystals  in  the  vicinity  of  salt 
lakes,  and  m  beds  associated  with  other 
lake  deposits  Its  crystals  ha\e  an  axial  ratio  5976:  i  •  i  2524 
They  are  commonly  prismatic  but  those 
from  California  are  tabular  and  are  bounded 
by  ooP(uo),  oP(ooi),  P(iiT),  £P  60(106), 
and  ooPw(ioo)  (Fig  131)  Twins  are 
common  (Fig  132) 

The  mineral  is  colorless,  white  or  reddish 
and  has  a  salty  taste  Its  hardness  is  2-3 
and  Its  specific  gravity  2  68  Its  inter- 
mediate refractive  index  is  i  470  It  is 
readily  soluble  in  water.  It  occurs  in  exten- 
sive deposits  in  the  Rio  Verde  Valley,  Ari- 
zona, and  as  crystals  at  Borax  Lake,  Cali- 
fornia and  on  the  shores  of  salt  lakes  in 
Central  Asia  and  South  America. 

FIG  132  —Thenardite 
Twinned  about  P  06  (on) 
Forms  same  as  m  Fig.  131 
and  oo  P  oo ,  100  (a) 



The  bante  group  includes  the  sulphates  of  the  alkaline  earths  and 
lead  They  are  all  light  colored  minerals  with  a  nonmetallic  luster 
They  all  crystallize  in  the  orthorhombic  system  (bipyramidal  class), 
and  all  have  a  hardness  of  about  4  The  minerals  comprising  this  group, 
with  their  axial  ratios,  are 

Anhydnte  CaSO*   a  •  b  :  c=  8932  '  i  •  i  0008 
Bante        BaS04  =8152    i     1 3136 

Celestite      SrS(>4  =  7790    i  .  i  2800 

Angleute    PbSQi  =  7852  :  i  .  i  2894 

Anhydrite  (CaSO4) 

Calcium  sulphate  is  dimorphous  The  natural  compound,  anhy- 
drite, is  orthorhombic  bipyramidal  In  addition  to  this,  there  is  another 
which  passes  over  into  anhydrite  when  shaken  for  a  long  time  with  boiling 
water  It  is  produced  by  dehydrating  gypsum  at  about  100°  When 
moistened  it  combines  with  water  and  passes  back  to  gypsum  It  is 
probably  tnclmic  It  is  unstable  under  the  conditions  prevailing  at 
the  earth's  suiface  and  is,  therefore,  not  found  as  a  mineral 

Anhydrite  occurs  usually  m  fibrous,  granular  or  massive  forms,  not 
often  in  crystals  When  crystals  occur  they  are  commonly  prismatic  or 
tabular  m  habit 

In  composition  the  mineral  is  58  8  per  cent  SOa  and  41  2  per  cent 

Its  crystals  are  usually  bounded  by  the  three  pinacoids  oP(ooi), 
oo  P  60(100),  oo  p  06(010)  and  P(ni),  2P2(i2i),  3P3(i3i),  POO(IOI) 
and  Poo  (on)  The  prismatic  types  are  usually  elongated  parallel  to 
the  macroaxis  The  angle  noAiTo=83°  41' 

Anhydrite  fuses  quite  easily  before  the  blowpipe  and  colors  the  flame 
reddish  yellow  It  is  very  slightly  soluble  in  water  but  is  completely 
dissolved  in  strong  sulphuric  acid  It  cleaves  parallel  to  the  three  pm- 
acoids  yielding  rectangular  fragments.  Its  hardness  is  3-3  5  and  den- 
sity about  2  93  Its  luster  is  vitreous  m  massive  pieces  and  its  color 
white,  often  with  a  distinct  tinge  of  blue,  gray  or  red.  In  small  frag- 
ments it  is  translucent,  but  in  large  masses  it  is  opaque  Its  refractive 
indices  for  yellow  light  are  «=  i  5693, 7=1  6130 

It  is  distinguished  from  the  other  sulphates  by  its  specific  gravity 
and  the  color  it  imparts  to  the  blowpipe  flame 


Synthesis  — Its  crystals  have  been  produced  by  slowly  evaporating  a 
solution  of  gypsum  in  HfoSCX 

Occurrence  — Anhydrite  occurs  as  crystals  implanted  on  the  minerals 
of  ore  veins,  cis  beds  of  granular  masses  associated  with  gypsum,  and  as 
crystalline  masses  in  layers  associated  with  rock  salt — the  two  having 
been  deposited  by  the  evaporation  of  salt  waters 

Localities  — The  mineral  is  found  at  the  salt  mines  of  Stassfurt,  in 
Germany,  Hail,  in  Tyrol,  Bex,  in  Switzerland,  in  the  ore  veins  of 
Andreasberg,  m  Harz,  Bleiberg,  m  Carmthia,  and  at  many  other  places 
m  Europe  At  Lockport,  N  Y  ,  and  at  Nashville,  Tenn  ,  it  occurs  as 
crystals  lining  geodes  m  limestone,  and  at  the  mouths  of  the  Avon  and 
St  Croix  Rivers  m  Nova  Scotia  it  forms  large  beds  associated  with 

Uses  — Finely  granular  forms  of  the  mineral  are  used  for  ornamental 
purposes,  and  as  a  medium  for  the  use  of  sculptors  The  massive  variety 
is  occasionally  employed  as  a  land  plaster  to  enrich  cultivated  soils 

Barite  (BaSO4) 

Bante,  or  heavy  spar,  usually  occurs  crystallized,  though  it  is  also 
often  found  massive  and  in  granular,  fibrous  and  lamellar  forms  It  is 
a  common  mineral  associated  with  sulphide  ores  as  a  gangue 

The  mineral  is  sometimes  pure  but  it  is  usually  intermixed  with  the 
isomorphous  calcium  and  strontium  sulphates  The  pure  mineral  con- 
tains 34  3  pei  cent  SOs  and  65  7  per  cent  BaO  As  usually  mined  it 
contains  SiOa,  CaO,  MgO,  AlgOa,  FegOa  and  in  some  instances  PbS2 

The  simple  crystals  are  usually  tabular  or  prismatic  in  habit.  The 
tabular  forms  are  commonly  bounded  by  oP(ooi),  ooP(no)  and  the 
domes,  P  66  (101),  |P  ob  (102),  2P  06  (021),  and  P  06  (on),  and  sometimes 
P(ni)  and  oo Poo  (100)  (Fig.  133),  The  prismatic  forms  are  usually 
elongated  m  the  direction  of 
the  a  axis,  and  are  bounded 
by  the  same  planes  as  the 
tabular  crystals  (Fig  134)  FlG  I33 —Bante  Crystals  with  oop,  J10  (m), 
Complex  crystals  are  also  iPoo,  102  (d),  PoS,oii  (0)  and  oP,  ooi  (c) 
abundant  They  are  often 

beautifully  supplied  with  planes,  the  total  number  known  on  the 
species  being  about  100     The  angle  noAiio^T80  22?' 

The  cleavage  of  bante  is  perfect  parallel  to  oP(ooi)  and  oo  P(no) 
It  is  brittle     Its  hardness  is  about  3  and  its  density  about  4  5     The 


mineral  is  white,  often  with  a  tinge  of  yellow,  biown,  blue,  01  red 
It  is  transparent  or  opaque  and  its  streak  is  white  Its  refi active 
indices  for  yellow  light  die  a=  i  6369,  7=  i  6491 

Before  the  blowpipe  bante  decrepitates  and  fuses,  at  the  same  time 

coloring  the  flame  yel- 
lowish green  The  fused 
mass  reacts  alkaline  to 

lltmus  paper    Jt  1S  m" 

The  mineral  barite  is 
FIG  134 -Bante  Crystals  with  m,  d,  o  and  c  as  m  distinguished   from    the 
Fig    133     Also  coPoo,  zoo  (a),   P,  m  60  and   ^ 

P2,  122  (y)  l  / 

high  specihc  gravity  and 

the  color  it  imparts  to  the  blowpipe  flame 

Syntheses  — Crystals  have  been  made  by  heating  precipitated  barium 
sulphate  with  dilute  HC1  in  a  closed  tube  at  150°,  and  by  cooling  a  fusion 
of  the  sulphate  in  the  chlorides  of  the  alkalies  or  alkaline  earths 

Occurrence  and  Origin — Bante  is  a  common  vein-stone  It  con- 
stitutes the  gangue  of  many  ore  veins,  particularly  those  of  copper, 
lead  and  silver.  It  is  found  also  as  a  replacement  of  limestone,  which, 
when  it  weathers,  leaves  the  barite  in  the  form  of  fragments  and  noduleb 
in  a  residual  clay,  and  as  a  deposit  in  hot  spnngs.  In  all  cases  it  is 
believed  to  be  a  deposit  from  solutions 

Localities  —Barite  occurs  abundantly  in  England,  Scotland,  and  on 
the  continent  of  Europe  Crystals  are  found  at  Cheshire,  Conn  ;  at 
DeKalb,  St  Lawrence  Co ,  N  Y  ,  at  the  Phoenix  Mine  in  Cxbarrus 
Co,,  N  C  ,  and  near  Fort  Wallace,  New  Mexico  Massive  barite  m 
pieces  large  enough  to  warrant  polishing  is  found  on  the  bank  of 
Lake  Ontario,  at  Sacketts  Harbor,  N  Y  It  constitutes  the  filling  of 
veins  at  many  different  places,  more  particularly  in  the  southern  Appa- 
lachians and  m  the  Lake  Superior  region, 

Preparation — Much  of  the  mineral  that  enters  the  trade  in  the 
United  States  is  obtained  from  the  deposits  in  residual  clay  The  rough 
material  is  washed,  hand  picked,  crushed,  ground  and  treated  with 
sulphuric  acid.  The  acid  dissolves  most  of  the  impurities  and  leaves 
the  powdered  mineral  white 

Uses  —The  white  varieties  of  the  mineral  are  ground  and  the  powder 
is  used  in  making  paints  The  mineral  is  also  employed  in  the  manu- 
facture of  paper,  oilcloth,  enameled  ware,  and  m  the  manufacture  of 
barium  salts,  the  most  important  of  which  is  the  hydroxide,  which  is 
employed  m  refining  sugar. 


The  colored  massive  varieties,  more  especially  stalactitic  and  fibrous 
forms,  are  sawn  into  slabs,  polished  and  used  as  ornamental  stones 

Production—  The  quantity  of  bante  mined  in  the  United  States 
during  1912  was  over  37,000  tons,  valued  at  $153,000  The  principal 
producing  states  are  Missouri,  Tennessee  and  Virginia.  The  imports 
in  the  same  year  were  about  26,000  tons  of  crude  material,  valued  at 
$52,467  and  3,679  tons  of  manufactured  material,  valued  at  $26,848 
Besides,  there  were  imported  $70,300  worth  of  artificial  barium  sul- 
phate and  about  $280,000  worth  of  other  barium  salts,  exclusive  of 

Celestite  (SrSO*) 

Celestite  occurs  in  tabular  prismatic  crystals,  in  fibrous  and  some- 
times in  globular  masses  Though  usually  white,  it  often  possesses  a 
bluish  tinge,  to  which  it  owes  its  name 

The  theoretical  composition  of  the  mineral  is  43  6  per  cent  80s 
and  56  4  per  cent  SrO,  but  it  often  contains  small  quantities  of  the 
isomorphous  Ca  and  Ba  compounds 

Many  celestite  crystals  are  very  similar  in  habit  to  those  of  bante. 

FIG.  135 —Celestite  Crystals  with  oo  p,  no  (w),  iPoo,  102  (<Q,  J  Poo,  104  (r), 
oo  P  oo ,  oio  (&),  P  oo ,  on  (0)  and  oP,  ooi  (c) 

Tabular  forms  are  perhaps  more  common  (Figs.  135),  Occasionally, 
pyramidal  crystals  are  bounded  by  PiJ(i44),  °oP^(ioo),  Poo  (on) 
and  oP(ooi)  These  often  have  rounded  edges  and  curved  faces  and 
thus  come  to  have  a  lenticular  shape.  The  angle  no  A  iTo= 75°  50' 

The  cleavage  of  the  mineral  is  perfect  parallel  to  oP(ooi)  and  almost 
perfect  parallel  to  oo  P(IIO)  Its  hardness  is  about  3  and  its  specific 
gravity  3  95.  Its  luster  and  streak  are  like  those  of  barite.  Its  color 
is  often  pale  blue  and  sometimes  light  red,  but  pure  specimens  are 
white  or  colorless.  Its  refractive  indices  for  yellow  light  are:  «=  i  6220, 
7=1  6237 

Before  the  blowpipe  celestite  reacts  like  barite  except  that  it  tinges 
the  flame  crimson  This  crimson  color  may  be  obtained  more  dis- 
tinctly by  fusing  a  little  powder  of  the  mineral  on  charcoal  in  the  reduc- 


mg  flame  and  dissolving  the  resulting  mass  in  a  small  quantity  of  hydro- 
chloric acid,  then  adding  some  alcohol  and  igniting  the  mixture 

Syntheses — Crystals  of  celestite  are  produced  in  ways  analogous 
to  those  in  which  bante  crystals  are  formed 

Occurrence  and  Ongin  —Celestite  occurs  in  beds  with  rock  salt  and 
gypsum,  as  at  Bex,  Switzerland,  associated  with  sulphur,  as  at  Gir- 
genti,  Italy,  and  in  crystals  and  grams  scattered  through  limestone, 
as  at  Strontian  Island,  Lake  Erie,  and  in  Mineral  Co ,  W  Va ,  or 
as  crystals  lining  geodes  in  the  same  rock  It  is  also  sometimes  found 
as  a  gangue  in  mineral  veins  In  some  instances  it  was  deposited  by 
hot  waters,  in  others  by  cold  waters,  and  in  others  it  was  concentrated 
by  the  leaching  of  strontium-bearing  limestones  by  atmospheric  water 

Production  and  Uses  — Although  the  mineral  occurs  in  large  quan- 
tity at  a  number  of  places  in  the  United  States  and  Canada  it  is  not 
mined  A  small  quantity  of  the  strontium  oxide  is  annually  imported 
Strontium  salts,  prepared  from  celestite  in  part,  aie  used  in  the  manu- 
facture of  fireworks  and  medicines  and  m  refining  sugar. 

Anglesite  (PbSOt) 

Anglesite  occurs  principally  as  crystals  associated  with  galena  and 
other  ores  of  lead,  but  is  found  also  massne,  and  in  granular,  stalactitic 
and  nodular  forms 

The  theoietical  composition  of  the  mineral  demands  73  6  per  cent 
PbO  and  26  4  S03 

Its  orthorhombic  crystals  are  usually  prismatic  or  isomctnc  in  habit 
Tabular  habits  are  less  common  than  in  bante  and  celestite  The 
principal  forms  occurring  are  ooPcfc  (100),  <*>P(iio),  iPoo  (102),  and 
other  macrodomes,  P  oo  (on)  and  various  small  pyramids,  with  oP(ooi), 
m  addition,  on  the  tabular  crystals  (Figs  ij6,  137,  138),  The  angle 
no  A  iTo=76°  i6J' 

The  cleavage  of  anglesite  is  distinct  parallel  to  oP(ooi)  and  oo  P(i  10) 
Its  fracture  is  conchoidal  The  mineral  is  white,  gray  or  colorless  and 
transparent,  and  is  often  tarnished  with  a  gray  coating.  It  has  an 
adamantine  or  residuous  luster,  is  bnttle  and  has  a  colorless  streak 
Its  hardness  is  2  5-3  and  sp  gr  6  3-6  4.  Impure  varieties  may  be 
tinged  with  yellow,  green  or  blue  shades  and  m  some  cases  may  be 
opaque  Its  refractive  indices  for  yellow  light  are  «=  i  8771,  7  « i  8937. 

Before  the  blowpipe  anglesite  decrepitates  It  fuses  m  the  flame  of 
a  candle  On  charcoal  it  effervesces  when  heated  with  the  reducing 
flame  and  yields  a  button  of  metallic  lead  In  the  oxidizing  flame  it 



gives  the  lead  sublimate     The  mineral  dissolves  m  HN03  with  dif- 

The  mineral  is  characterized  by  its  high  specific  gravity  and  the 

FIG  136  FIG  137 

FIG    136  — Ynglesilc  Crystal  with    w  P,  no  (m),    ooPw,  100  (a),    oP,  ooi  (c), 

JP,  112  (/)  and  Pi,  122  (y) 

FIG     137  —  \nglcsitc  Crystal   with  /;/,  a  and  y  as  in  Fig    136     Also    oopoo, 
cio  (bj,  P  oo  ,  on  (o),  P,  in  (s)  and  JP  oo ,  102  (d) 

reaction  for  lead.    It  is  distinguished  from  (.erussrte  by  the  reaction  for 
sulphur  and  the  lack  of  effervescence  with  HC1 

Syntheses  — Crystals  of  anglesite  have  been  made  by  methods  anal- 
ogous to  those  used  in  the  preparation  of  bante  crystals 

Occurrence  — The  mineral  occurs  as  an  alteration  product  of  galena, 

mainly  in  the  upper  portions  of  veins  of  

lead  ores  Under  the  influence  of  solu- 
tions of  carbonates  it  changes  to  cerus- 

Localities —It  is  found  in  Derby- 
shire and  Cumberland,  in  England, 
near  Siegen,  in  Prussia,  m  Australia  and 
in  the  Sierra  Mojada,  m  Mexico  In  the 
United  States  crystals  occur  at  Phoenix- 

ville,  Penn  ,  in  the  lead  districts  of  the  Mississippi  Valley,  and  at 
various  points  in  the  Rocky  Mountains 

Use*. — It  is  mined  with  other  lead  compounds  as  an  ore  of  this  metal 


Although  several  basic  sulphates  are  known  as  minerals,  only  two 
are  of  importance  One,  brochantite,  is  a  copper  compound  found,  with 
other  copper  minerals,  in  the  oxidized  portions  of  ore  veins,  and  the 
other,  alumte,  is  a  double  salt  of  aluminium  and  potassium.  This  min- 

FIG  138 —Anglesite  Crystal  with 
m,  y,  c  and  d  as  in  Figs  136  and 
137  Also  iP  63 ,  104  (Q  and  P?, 
144  (x) 


eral  is  one  of  a  series  of  compounds  forming  an  isomorphous  group,  with 
the  general  formula  (R'"(OH)2)6R'2(S04)4  or  (R'''(OH)2)oR''(SOi)i, 
in  which  R'"=A1  or  Fe,  R'2=K2,  Na2  or  H2  and  R"=Pb 

Alumte  ((A1(OH)2)6K2(S04)4) 

Alunite,  or  aiumstone,  is  a  comparatively  rare  mineral,  but,  because 
of  its  possible  utilization  as  a  source  of  potash,  it  is  of  considerable  in- 
terest It  has  long  been  used  abroad  as  a  source  of  potash  alum 

The  mineral,  when  pure,  contains  38  6  per  cent  863,  37  o  per  cent 
Al20s,  ii  4  per  cent  K20  and  13  o  per  cent  EkO,  which  corresponds  to 
the  formula  given  above,  or  if  written  in  the  form  of  a  double  salt 
3(A1(OH)2)2S04  K2S04  The  chemical  composition  of  a  crystalline 
specimen  from  Marysville,  Utah,  is  as  follows 

S03    Al20j  Fe203  P20f,  K20  Na20  H20+  H20-  Si02        Total 
38  34    37  18      tr      58    xo  46      33      12  90       09       22        too  10 

Alunite  occurs  in  hexagonal  crystals  (ditrigonal  scalenohedral  class), 
with  an  axial  ratio  of  i  i  252  The  natural  crystals  are  nearly  always 
simple  rhombohedrons,  R(ioTi),  or  R  modified  by  other  rhombohedrons 
and  the  basal  plane  Because  the  angle  between  the  rhombohcdral 
faces  is  about  90°  (90°  50')  ,  the  habit  of  the  crystals  is  cubical  The 
mineral  also  occurs  massive,  with  fibrous,  granular  or  porcelain-like 

Alunite  is  white,  pink,  gray  or  red,  and  has  a  white  streak  It  is 
transparent  or  translucent  and  has  a  vitreous  or  nearly  pearly  luster. 
Its  cleavage  is  distinct  parallel  to  oP(oooi),  and  it  has  an  uneven,  con- 
choidal  or  earthy  fracture  Its  hardness  ib  3  5-4  and  its  density  = 
26-275.  Its  indices  of  refraction  for  yellow  light  are:  €sasiS92, 
<o=i  572 

Before  the  blowpipe  the  mineral  decrepitates,  but  is  infusible  In 
the  closed  tube  it  yields  water  and  at  a  high  temperature  sulphurous  and 
sulphuric  oxides  Heated  on  charcoal  with  Co(NOs)2  it  gives  the  blue 
color  characteristic  of  Al20a  It  also  gives  the  sulphur  reaction  It  is 
insoluble  in  water  but  is  soluble  in  H2S04  When  ignited  it  gives  off 
all  its  water  and  three-quarters  of  its  S04,  the  other  quarter  remaining 
in  &2S04  When  the  igmted  residue  is  treated  with  water,  the  potas- 
sium sulphate  dissolves  and  insoluble  Al20s  is  left.  It  is  upon  this 
latter  reaction  that  the  economic  utilization  of  the  mineral  depends, 

The  mineral  is  characterized  by  its  color  and  hardness  together 
with  the  reactions  for  AljHgO  and  sulphuric  acid 


Synthesis  — Crystals  have  been  made  by  heating  an  excess  of  alu- 
minium sulphate  with  alum  and  water  at  230° 

Occurrence  anl  Ongm— The  mineral  occurs  m  seams  or  veins  in 
acid  lavas  It  is  thought  to  have  been  formed  in  some  instances  by 
the  action  of  sulphurous  vapors  upon  the  rock  forming  the  vein  walls, 
in  other  instances  by  direct  precipitation  from  ascending  magmatic 
waters,  and  in  others  by  the  action  of  descending  BfeSC^ 

Localities — The  principal  known  occurrences  of  alumte  are  at 
Tolfa,  Italy,  at  Bulla  Delah,  New  South  Wales,  on  Milo,  Grecian 
Archipelago,  and  at  Mt  Dore,  France 

In  the  United  States  it  is  found  with  quartz  and  kaolin  in  the 
Rosita  Hills,  and  the  Rico  Mts,,  Colo  ,  in  the  ore  veins  at  Silverton 
and  Cripple  Creek,  Colo  ,  as  a  soft  white  kaolin-like  material  in  the 
ore  veins  at  Goldfield,  Nev  ,  as  a  crystalline  constituent  in  the  rocks 
at  Goldfield,  Nev ,  and  Tres  Cerntos,  Cal ,  and  in  the  form  of  a  great 
vein  of  comparatively  pure  material  at  Marysville,  Utah 

Uses  — In  Australia  alumte  is  calcined  and  then  heated  with  dilute 
sulphuric  acid.  The  mixture  is  then  allowed  to  settle  and  the  clear 
solution  is  drawn  off  and  cooled  Alum  crystallizes  The  mother  liquor 
which  contains  aluminium  sulphate,  after  further  treatment  with  the 
calcined  mineral,  is  evaporated  and  the  aluminium  salt  separated  by 
crystallization  In  the  United  States  it  is  now  (1916)  being  utilized 
as  a  source  of  potash  and  aluminium 

Brochantite  ((CuOH)2S04  2Cu(OH)2)  occurs  in  groups  of  small 
prismatic  crystals,  in  fibrous  masses  and  in  drusy  crusts  Its  crystal- 
lization is  orthorhombic  with  a  b  •  £-.7739  •  i  ;  4871  and  the  angle 
1 10  A  no  =75°  28'  Cleavage  is  perfect  parallel  to  oopas  (oio).  The 
mineral  is  emerald-green  to  blackish  green  and  its  streak  is  light 
green.  It  is  transparent  or  translucent,  and  its  luster  is  vitreous, 
except  on  cleavage  planes  where  it  is  slightly  pearly  Its  hardness  is 
3  5-4  and  density  3  85  In  the  closed  tube  it  decomposes,  yielding 
water  and,  at  a  high  temperature,  sulphuric  acid.  It  gives  the  usual 
reactions  for  copper  and  sulphuric  acid  Brochantite  occurs  in  the 
upper  portions  of  copper  veins  at  many  places,  in  some  of  which  it  was 
formed  by  the  interaction  between  silicates  and  solutions  of  copper 
salts.  In  the  United  States  it  has  been  foi}nd  at  the  Monarch  Mine, 
Chaffee  Co ,  Colorado,  at  the  Mammoth  Mine,  Tmtic  District,  Utah, 
and  in  the  Clifton-Morenci  Mines,  Arizona, 



The  hydrous  sulphates  comprise  a  numbei  of  sulphates  combined 
with  water  Among  them  are  the  normal  salts  miralnhte  or  glauber 
salt  (Na2S04  loEfeO),  gypsum  (CaSQi  2H/)),  the  epwmilc  and  inclan- 
tertte  groups  (R//S04  7H20),  chakanttnte  (CuS04  sEbO),  «md  the 
alum  group  (R'A1(S04)2  i2H20),  kiesente  (MgSOi  H2O),  polyhalite 
(K2MgCa2(S(X)4  H20),  and  a  number  of  basic  compounds  Several 
of  them  are  of  considerable  economic  importance,  They  are  separated 
into  a  normal  group  and  a  basic  group, 


The  hydrated  normal  sulphates  occur  in  crystals,  and  most  of  them 
are  found  also  in  beds  mterstratified  with  other  compounds  that  arc 
known  to  have  been  precipitated  by  the  evaporation  of  sea  water  or  the 
water  of  salt  and  bitter  lakes  All  are  soluble  in  water 

Mirabdite,  or  glauber  salt,  (Na2SOt  loHaO)  is  a  white,  trans- 
parent to  opaque  substance  occurring  m  monoclmic  crystals  or  as 
efflorescent  crusts  Its  hardness  is  i  5-2  and  specific  gravity  i  48  It 
is  soluble  in  water  and  has  a  cooling  taste  When  exposed  to  the  air  it 
loses  water  and  crumbles  to  a  powder  Mirabihte  occurs  at  the  hot 
springs  at  Karlsbad,  Bohemia  and  is  obtained  from  the  water  of  many 
of  the  bitter  lakes  m  California  and  Nevada  Its  crystals  are  deposited 
from  a  pure  solution  of  Na2S04  If  the  solution  contains  NaCl,  how- 
ever, thenardite  (Na2S04)  deposits 

Kieserite  (MgS(>4  H20)  occurs  commonly  m  granular  to  compact, 
massive  beds  mterstratified  with  halite  and  other  soluble  salts  at  Stass- 
furt,  Germany,  and  at  other  places  where  ocean  water  has  been  evap- 
orated. It  is  believed  to  have  resulted  from  the  partial  desiccation  of 
epsomite  (MgS04  ?H20),  though  it  may  be  deposited  from  a  solution 
of  MgSO*  m  the  presence  of  MgCfe.  Kiesente  is  white,  gray,  or  yellow- 
ish, and  is  transparent  or  translucent  It  forms  sharp  bipyraimdal 
monoclmic  crystals  Its  hardness  is  3  and  its  density  2  57*  In  the 
presence  of  water  it  passes  over  into  epsomite  and  dissolves,  yielding  a 
solution  with  a  bitter  taste.  Large  quantities  are  utilized  in  the  fer- 
tilizer industry 

When  exposed  to  the  air  it  becomes  covered  with  aa  opaque  crust* 



Gypsum  (CaSO4  2H20) 

Gypsum  is  the  most  important  of  all  the  hydrous  sulphates  It 
occurs  in  massive  beds  a'vociated  with  limestone,  m  crystals,  in  finely 
granular  aggregates  and  in  fibrous  masses,  under  a  great  variety  of 

Theoretically,  it  consists  of  46  6  per  cent  80s,  32  5  per  cent  CaO  and 
20  9  per  cent  EfeO,  but  usually  it  contains  also  notable  quantities  of  other 
components,  especially  Fe203,  AbOa  and  8162  Clay  is  a  common  im- 
purity in  the  massive  varieties 

The  analyses  of  two  commercial  gypsums  follow 

CaSCXt  H20  Si02  A1203  CaC03  MgC03  Total 
78  40  19  96  35  12  56  57  99  96 
78  51  20  96  05  08  ii  99  71 

Dillon,  Kans 
Alabaster,  Mich 

The  crystals  are  monoclmic  (prismatic  class),  with  a  :  b  •  ^=.6895  : 
i  •  4132  and  j8=8i°  02'     They  are  usually  developed  with  a  tabular 
habit  due  to  the  predominance  of  oo  P  OD  (oio)     The  prism  oo  P(iio), 

FIG  139  FIG  140 

FIG  139 — Gypsum  Crystals  with  wP,  no  («),    ooPoo,  oio  (ft),   —  P,  in  (/)  and 

FIG    140  — Gypsum  Twinned  about  oo  P  55   (100)     Swallow-tail  Twin     Form  mt 

I  and  b  as  in  Fig  139 

and  pyramid  +P(ixI)  are  also  nearly  always  present  (Fig  139).  Often 
the  +P  faces  are  curved,  producing  a  lens-shaped  body  Twinning  is 
very  common,  giving  rise  to  two  types  of  twinned  crystals  In  the  most 
common  of  these  oo  P  56  (100)  is  the  twinning  plane  and  the  resulting 
twin  has  the  form  of  Fig  140  In  the  second  type -P  66  (101)  is  the 
twinning  plane  (Fig.  141)  Forms  of  this  type  are  frequently  bounded 
by  +P(iiT),  -P(iii),  |P  oo  (103),  and  °OP65  (100)  When  the  side 



faces  are  curved  the  well  known  arrowhead  twins  result  (Fig   141) 

The  angle  noAiTo=68°  30' 

The  mineral  possesses  a  good  cleavage  parallel  to    oo  P  $>  (oio) 

yielding  thin  inelastic  fohae,  another  parallel  to  +P(Tn)  and  a  less 

perfect  one  parallel  to  oo  P  66  (100) 
It  is  white,  colorless  and  transpar- 
ent when  pure,  gray,  icd,  yellow, 
blue  or  black  when  impure  Its 
hardness  is  i  5-2  and  sp.  gr  =2  32 
The  luster  of  crystals  is  pearly  on 
oo  P  ob  (oio)  and  on  other  surfaces 
vitreous  Massive  varieties  are  often 
dull  The  refractive  indices  for  yel- 
low light  are,  a=  1.5205,  0=  1.5226, 

FIG    141— Gypsum    Twinned    about  ^*~J  S29 

-P«5(ioi)  Forms  <*>POO,  100  In  the  closed  tube  the  mineral 
(a),  -P,  in  (/),  P,  nl  («)  and  gives  off  watei  and  falls  into  a  white 
J  P  55 ,  Io3  (e)  Arrow  head  Twm  powder  (see  p  238)  It  colors  the 

flame  yellowish  red  and  yields  the  sul- 
phur test  on  a  silver  coin.  It  is  soluble  m  about  450  pts  of  water  and 
is  readily  soluble  in  HC1  When  heated  to  between  222°  F  and  400°  F 
it  loses  water  and  disintegrates  into  powder,  which,  when  ground, 
becomes  "  plaster  of  Pans  "  This,  when  moistened  with  water,  again 
combines  with  it  and  forms  gypsum  The  crystallization  of  the  mass 
into  an  aggregate  of  interlocking  crystals  constitutes  the  "  set." 

Gypsum  is  distinguished  from  other  easily  cleavable,  colorless  min- 
erals by  its  softness  and  the  reactions  for  S  and  EfeO. 

The  varieties  of  gypsum  generally  recognued  are. 

Syenite,  the  transparent  crystallized  variety, 

Safanspar,  a  finely  fibrous  variety, 

Alabaster,  a  fine-grained  granular  variety,  and 

Rock-gypsum,  a  massive,  structureless,  often  impure  and  colored 

Gypsiie  is  gypsum  mixed  with  earth 

Syntheses  — Crystals  of  gypsum  separate  from  aqueous  solutions  of 
CaSO*  at  ordinary  temperatures,  and  also  from  solutions  saturated 
with  Nad  and  MgCk  Some  of  these  are  twinned. 

Occurrence  and  Origin — Gypsum  forms  immense  beds  interstrati- 
fied  with  limestone,  clay  and  salt  deposits  where  it  has  been  precipitated 
by  the  evaporation  of  salt  lakes  Its  crystals  occur  around  volcanic 
vents,  where  they  are  produced  by  the  action  of  sulphuric  acid  on  cal- 


careous  rocks.  They  are  also  found  isolated  in  clay  and  sand,  and  in 
limestone,  wherever  this  rock  has  been  acted  upon  by  the  sulphuric  acid 
resulting  from  the  weathering  of  pynte  Gypsum  also  occurs  in  veins 
and  is  found  in  New  Mexico  in  the  form  of  hills  of  wind-blown  sand 

Localities  — Crystals  are  found  m  the  salt  beds  at  Bex,  Switzerland, 
in  the  sulphur  mines  at  Girgenti,  Sicily,  and  at  Montmar-tre,  France 
In  the  United  States  they  occur  at  Lockport,  N  Y ,  in  Trumbull  Co , 
Ohio,  and  in  Wayne  Co ,  Utah,  in  limestone,  and  on  the  St  Mary's 
River,  Maryland,  in  clay 

Extensive  beds  occur  in  Iowa,  Michigan,  New  York,  Virginia,  Ten- 
nessee, Oklahoma  and  smaller  deposits  in  many  other  states,  and  wind- 
blown sands  in  Otero  Co  ,  New  Mexico 

Uses  — Crude  gypsum  is  used  in  the  manufacture  of  plaster,  as  a 
retarder  in  Portland  cement,  and  as  a  fertilizer  under  the  name  of  land 
plaster  The  calcined  mineral  is  used  as  plaster  of  Pans  and  in  the 
manufacture  of  various  wall  finishing  plasters,  and  certain  kinds  of 
cements  Small  quantities  are  used  in  glass  factories,  and  as  a  white- 
wash, a  deodorizer,  to  weight  phosphatic  fertilizer,  as  an  adulterant  in 
candy  and  other  foods,  and  as  a  medium  for  sculpture 

Production — The  quantity  of  gypsum  mined  in  the  United  States 
during  1912  aggregated  2,500,757  tons,  valued  at  $6,563,908  in  the  form 
in  which  it  was  sold  Of  this  amount,  441,600  tons  of  crude  material, 
valued  at  $623,500  were  sold  ground,  and  1,731,674  tons,  valued  at  $5,- 
940,409,  were  calcined  The  output  of  New  York  was  valued  at  $1,241,- 
500,  that  of  Iowa  at  $845,600  and  of  Ohio  at  $812,400 

After  the  United  States  the  next  largest  producer  is  France  with  a 
product  in  1910  of  1,760,900  tons,  valued  at  $2,942,600  and  Canada  with 
525,246  tons,  valued  at  $934,446 


These  groups  comprise  minerals  with  the  general  formula  RSO-i  7HkO, 
in  which  R=Mg,  Zn,  Fe,  Ni,  Co,  Mn  and  Cu  Isomorphous  mix- 
tures indicate  that  the  compounds  are  diomorphous,  and  that  the 
group  is,  therefore,  an  isodimorphous  group.  The  group  is  separable 
into  two  divisions,  of  which  one,  the  epsomite  group,  crystallizes  in  the 
bisphenoidal  class  of  the  orthorhombic  system  with  axial  ratios  approx- 
imating i  :  i  '  ,565  The  other  division,  the  vUriol9  or  mdanterite, 
group  crystallizes  in  the  prismatic  class  of  the  monochmc  system  with 
axial  ratios  approximating  1 18  '  i '  i  53  and  ft  approximating  75° 
Only  the  magnesium  compound  among  the  pure  salts  is  known  to  crys- 
tallize in  both  systems.  Crystals  separated  from  a  saturated  solution 


are  orthorhombic,  while  those  separated  from  a  supersaturated  solution 
are  monoclimc  Other  salts  occur  in  isomorphous  mixtures  in  both 
systems  All  members  of  the  group  are  soluble  in  water  and  all  occur  as 
secondary  products  formed  by  decomposition  of  other  minerals. 

Epsomite  (MgSO4  7H20) 

Epsomite,  or  Epsom  salt,  usually  occurs  in  botryoidai  masses  and 
fibrous  crusts  coating  various  rocks  over  which  dilute  magnesium  sul- 
phate solutions  trickle,  and  mingled  with  earth 
in  the  soils  of  caves  The  solutions  result  from 
tke  act10n  upon  magnesian  rocks  of  sulphuric 
c,cid  derived  from  oxidumg  sulphides  Crys- 
tals are  rare 

The  composition  corresponding  to  MgSOr 
yHkO  demands  32,5  SOa,  163  MgO  and  51  2 

The  mineral  forms  white  or    colorless  bi- 
Ho  142-EpsomitcCrys-  sphenoidalj    orthorhombic    crystals,    with    an 
tal   with    OQ  P    1 10  (m)  ,        ,  .  -,, 

p  axial  ratio  a    b '  c=  9901     i     S7°9      Their 

and  -r,  in  (s)  habit  is  tetragonal     The  angle  no  A  1^0=89° 

26'     The  commonest  forms  occurring  on  syn- 

P  P 

thetic  crystals  are  combinations  of  ooP(iio),  and  -T(III)  or  -~J(ni) 

2  2 

(Fig  142)  Natural  crystals  contain,  m  addition  oo  P  56  (oio)  and 

The  luster  of  epsomite  is  vitreous,  its  hardness  2  0-2  5  and  specific 
gravity  170  Its  refractive  indices  for  yellow  light  are  a —143  25, 
0=i  4554  and  7=  i  4°°8 

The  mineral  is  soluble  m  water,  yielding  a  solution  with  a  bitter  taste 
With  a  solution  of  barium  chloride  it  yields  a  white  precipitate  of  BaSOt 

Epsomite  is  distinguished  from  other  colorless,  soluble  minerals  by 
its  taste  and  the  reactions  for  S  and  Mg 

Synthesis  —Crystals  are  produced  by  evaporation  of  solutions  of 
MgSO*  containing  certain  other  salts  From  those  containing  borax, 
crystals  of  the  type  indicated  above  are  separated  The  production  ot 
right  or  left  crystals  may  be  provoked  by  inoculation  of  the  solution  with 
a  particle  of  a  crystal  of  the  desired  type 

Locakties  — Epsomite  occurs  m  mineral  waters,  as,  for  instance,  at 
Seidlitz,  Bohemia,  on  the  walls  of  mines  and  caves,  among  the  deposits 
of  bitter  lakes,  and  as  crystals  m  the  soil  covering  the 'floors  of  caves 


Melantente,  01  copperas  (FeSO4  7H20),  is  usually  m  fibrous, 
stalactitic  or  pulverulent  masses  associated  with  pynte  or  other  sul- 
phides containing  iron,  from  which  it  was  produced  by  weathering 
processes  It  is  commonly  some  shade  of  green  Its  streak  is  colorless 
Its  crystals,  which  are  monochmc  (prismatic  class),  are  rare  The 
mineral  has  a  hardness  of  2  and  a  density  of  i  9  It  is  soluble  in  water, 
forming  a  solution  which  has  a  sweetish  astringent  taste. 


The  alum  group  includes  a  large  number  of  isomorphous  compounds 
with  the  general  formula  R'A1(S04)2  laHsO  The  group  crystallizes 
in  the  isometric  system  (dyakisdodecahedral  class),  but  all  of  its  mem- 
bers are  so  readily  soluble  m  water  that  they  are  rarely  found  in  nature 
The  commonest  alums  are  kalmite  (KA1  (864)2  I2H20)  and  soda  alum 


A  number  of  compounds  of  sulphates  with  chlorides  and  carbonates 
are  known,  but  of  these  only  one  is  of  any  great  economic  importance 
Two  others  afford  interesting  crystals  The  commercial  compound  is 
kaimte,  which  is  a  hydrated  combination  of  MgS04  and  KC1,  with 
the  formula  M&S04  KC1  3H20  The  other  two  best  known  members 
of  the  group  are  leadhillile  (PbSO4  Pb(PbOH)2(COs)2  and  hanksite 
(2Na2C03  QNa2S04  KCI) 

Kainite  (MgSO4  KCI  3H20) 

Kaimte  is  found  only  in  beds  associated  with  halite  and  other  deposits 
from  saline  waters  It  is  rarely  crystallized  Crystals  are  monoclmic 
(prismatic  class),  with  a  b  c=i  2186  :  i  .  5863  and  £=85°  6'.  They 
possess  a  pyramidal  habit  with  oP(ooi)  and  dbP(ni)(iiT)  predom- 

The  mineral  usually  forms  granular  masses  which  are  white,  yellow, 
gray  or  red  It  is  transparent,  has  a  hardness  of  2  and  sp  gr  2.13, 
and  is  easily  soluble  in  water  Its  refractive  indices  for  sodium  light  are- 
01=14948  and  7*1.5203 

When  heated  in  a  glass  tube  it  yields  water  and  HC1  It  is  distin- 
guished from  other  soluble  minerals  by  this  reaction,  and  by  the  fact 
that  it  yields  the  test  for  sulphur,  and  colors  the  flame  blue  when  its 
powder  is  mixed  with  CuO  and  heated  before  the  blowpipe 


Synthesis  — Crystals  have  been  produced  by  evaporating  a  solution 
of  K2S04  and  MgSOi  containing  a  great  excess  of  MgCb 

Occurrence  — Kaimte  occurs  in  the  salt  beds  of  Stassfurt,  Germany, 
and  of  Kalusz  in  Gahcia,  and  in  the  deposits  of  salt  lakes  and  lagoons 
It  also  occurs  as  crusts  on  some  of  the  lavas  of  Vesuvius 

Uses.— The  mineral  is  utilized  as  a  source  of  potassium  m  the  manu- 
facture of  potassium  salts  and  fertilizers  Large  quantities  are  imported 
annually  into  the  United  States  In  1912  the  imports  aggregated 
485,132  tons,  valued  at  $2,399,761 

Hanksite  (2Na2CO3  pNa2SOi  KC1)  occurs  almost  exclusively  in 

.  hexagonal  prisms  that  are  prismatic  or  tabular, 

or  in  double  pyramids  suggesting  quartz  crys- 
tals    Their  axial  ratio  is  i  .  i  006    The  com- 
monest  crystals  are   bounded   by   oP(oooi), 
FIG   143— Hanksite  Crys-    ooP(ioTo),  P(ioTi)  (Fig.  143)  and  2P(202i), 
tal  with  OOP,  joio  (w),  or  |p(4o4s)       Their   cleavage   is   imperfect 
P,  ion  (0)  and  oP,  oooi   p^M  ^  op(oool)      Thc  mmeml  fe  whjte  Qr 

yellow  Its  hardness  -2  and  its  specific 
gravity  =256  It  is  soluble  m  water.  Its  refractive  indices  are 
w=i  4807  and  €=i  4614  It  occurs  at  Borax  Lake  and  Death  Valley, 
California,  in  the  deposits  of  salt  lakes 

LeadhUlite  (PbSO4  Pb(PbOH)2(CO,<02)  occurs  principally  as 
crystals  m  the  oxidized  zones  of  lead  and  silver  veins  The  crys- 
tals are  monoclmic  (prismatic  class),  and  have  an  hexagonal  habit. 
Their  axial  ratio  is  i  7515  11:2  2261.  j9=89°32'.  The  principal 
forms  observed  on  them  are  oP(ooi),  oo'P(no),  ooP<w  (too),  P(m) 
and  £P6o  (102)  In  the  most  common  twins  ooP(no)  is  the  twin- 
ning plane  The  mineral  is  white  or  yellow,  green  or  gray,  and  it  is 
transparent  or  translucent  Its  streak  is  colorless  It  is  sectile,  has  a 
hardness  of  2  5  and  a  specific  gravity  of  6.35  Before  the  blowpipe  it 
mtumesces,  turns  yellow,  and  fuses  easily  (i  5)  Upon  cooling  it  again 
becomes  white  It  effervesces  m  HNOs  and  leaves  a  white  precipitate 
of  PbS04  It  reacts  for  sulphur  and  water  It  is  found  at  Leadhills, 
Scotland,  and  Mattock,  England,  associated  with  other  ores  of  lead; 
at  a  lead  mine  near  Iglesias,  Sardinia,  and  at  several  silver-lead  mines 
in  Arizona. 




The  only  chromate  of  importance,  among  minerals,  is  the  lead  salt  of 
normal  chromic  acid,  HkCrO*  There  are  several  other  chromates 
known,  but  they  are  basic  salts  and  are  rare  All  are  lead  compounds 
The  normal  salt,  PbCrO*,  is  known  as  crocoite  Chromic  acid  is  un- 
known, as  it  spontaneously  breaks  down  into  CrOa  and  water  when  set 
free  from  its  salts  Its  best  known  compound  is  potassium  chromate, 

Crocoite  (PbCr04) 

Crocoite  is  well  characterized  by  its  hyacinth-red  color     It  is  a  lead 
chromate  with  PbO=68  9  per  cent  and  003=31  i  per  cent. 

Its  crystallization  is  monoclmic 
(prismatic  class)  with  a  .  b  :  c 
=  9603  :  i  .  9159  and  0=77°  33'- 
Its  crystals,  which  are  usually  im- 
planted on  the  walls  of  cracks  in 
rocks,  are  prismatic  or  columnar 
parallel  to  ooP(no)  Their  pre- 
dominant forms  are  ooP(no), 
—  P(iu),  and  various  domes  (Fig 
144).  Their*  cleavage  is  distinct 
parallel  to  ooP(uo)  The  angle 
1  10  A  no=860  19'  The  mineral 
also  occurs  in  granular  masses 

Crocoite  is  bright  hyacinth-red, 
and  is  translucent  Its  streak  is 
orange-yellow  The  mineral  is  sec- 
tile  Its  fracture  is  conchoidal,  its 
hardness  2.5-3  and  density  about  6 
is  about  2  42, 

In  the  closed  tube  it  decrepitates,  and  blackens,  but  it  reassumes  its 
red  color  when  heated     On  charcoal  it  deflagrates  and  fuses  easily, 


FIG  144 —Crocoite  Crystals  with  «>P, 
no  (m),  cop},  120  (/),  -P,  in  0), 
3Po5,  301  (*),  PS5,  Tor  (£),  oP, 

001   (C),    P«>,OII   (*),    2?  CO,  021   (?) 

and  iPSb,oi2  (w) 

Its  intermediate  refractive  index 


yielding  metallic  lead  and  a  lead  coating  With  minocosmic  salt  it 
gives  the  green  bead  of  chromium 

The  mineral  is  easily  lecogmzed  by  its  color  and  the  test  for  chro- 

Synthesis  —  Crystals,  like  those  of  crocoite,  have  been  obtained  by 
heating  on  the  water  bath  a  solution  of  lead  nitrate  in  nitric  acid  and 
adding  a  dilute  solution  of  potassium  bichromate 

Occurrence  —  Crocoite  occurs  under  conditions  which  suggest  that  it 
is  a  product  of  pneumatolysis 

Locahhes  —  It  is  found  in  the  Urals,  at  Rezbanya  and  Moldawa,  m 
Hungary,  m  Tasmania,  and  m  the  Vulture  Mining  district,  Mancopa 
Co  ,  Arizona, 


The  tungstates  are  salts  of  tungstic  acid,  EfoWC^  They  are  the 
principal  sources  of  the  metal  tungsten  which  is  beginning  to  have  im- 
portant uses  The  molybdates  are  salts  of  molybdic  acid,  liaMoOt 
The  two  most  prominent  tungstates  arc  ideditc,  CaWQi,  and  wolf- 
ramite (Fe  Mn)W04,  and  the  most  prominent  molybdate  is  wulfenite, 

All  tungsten  compounds  give  a  blue  bead  with  salt  of  phosphorus  in 
the  reducing  flame  When  fused  with  NagCOa,  dissolved  in  water 
and  hydrochlonc  acid,  and  treated  with  metallic  zinc  (see  pp  482,  and 
492  for  details  of  test),  they  also  yield  a  blue  solution  which  rapidly 
changes  to  brown 

The  molybdates  give  with  the  salt  of  phosphorus  bead  in  the  oxidis- 
ing flc,me  a  yellow-green  color  while  hot,  changing  to  colorless  when  cold. 
In  the  reducing  flame  the  color  is  clear  green. 


The  scheelite  group  comprises  a  series  of  tungstates  and  molybdates 
of  Ca,  Cu  and  Pb  The  minerals  arc  tetragonal  and  hcmihcdral  and 
are  all  well  crystallized  The  more  important  members  of  the  group 
are  scheehte  and  wulfemte  CuprotungMe  is  a  copper  tungstate  (CuW04) 
and  stolzite  a  lead  tungstate 


The  formula  of  scheelite  demands  80  6  per  cent  WO.?,  and  194  per 
cent  CaO,  but  the  mineral  usually  contains  a  little  molybdenum  in 
place  of  some  of  the  tungsten  It  nearly  always  contains  also  a  little  Fe. 


Scheehte  crystallizes  in  the  tetragonal  bipyraimdal  class  Its  crys- 
tals are  usually  pyramidal,  though  often  tabular  m  habit  Their  axial 
ratio  is  i  :  i  5268  On  the  pyramidal  types  the  predominant  planes 
are  pyramids  of  the  first,  second  (Fig  145),  and  third  orders  and  on  the 
tabular  types,  in  addition,  the  basal  plane  One  of  the  most  familiar 

combinations  is  P(m),P  co  (101),   y  (313)  and  |  ^lj(i3i)  (Fig  145), 

Other  forms  frequently  found  on  its  crystals  are  |P  oo  (102)  and  £P  °° 
(105)  The  angle  no  A  In  =  79°  SSi'  Twinning  is  common,  both 
contact  and  penetration  twins  having  oo  p  oo  (100)  as  the  twinning 
plane  The  mineral  aJbO  occurs  m  remform  and  granular  masses 

Scheehte  is  white,  yellow,  brown,  greenish  or  reddish,  with  a  white 

FIG  145  FIG  146 

FIG  145  —  SdiceliLc  CryoUl  with  P,  in  \pjt  P  oo  ,  101  (e)  and  oP,  ooi  (c), 
FIG   146  —  Scheehte  Crybtal  with  1>  and  e  as  in  Fig  145     Also  I  ~  I  ,  313  (h)  and 

streak  and  vitreous  luster  It  has  a  distinct  cleavage  parallel  to  P(ooi), 
and  an  uneven  fracture  It  is  brittle,  has  a  hardness  of  4  3-5  and  a 
density  of  about  6,  and  is  transparent  or  translucent  It  is  soluble  in 
HC1  and  HNOs  with  the  production  of  a  yellow  powder,  tungsten  tri- 
oxide,  which  is  soluble  m  ammonia  Its  refractive  indices  are  €=  i  9345, 
w=  i  9185  for  red  light 

Before  the  blowpipe  the  mineral  fuses  to  a  semitransparent 
glass  With  borax  it  forms  a  transparent  glass  which  becomes  opaque 
on  cooling  With  salt  of  phosphorus  it  yields  the  characteristic  beads 
for  tungsten,  but  specimens  containing  iron  must  be  heated  with  tin  on 
charcoal  before  the  blue  color  can  be  developed 

Scheehte  is  distinguished  from  limestone,  which  its  massive  forms 
closely  resemble,  by  its  higher  specific  gravity  and  the  absence  of  effer- 


vescence  with  HC1  From  quartz  it  is  distinguished  by  its  softness  and 
from  bante  by  greater  hardness  and  higher  specific  gravity 

Syntheses  —Crystals  of  scheehte  have  been  made  by  adding  a  solu- 
tion of  sodium  tungstate  to  a  hot  acid  solution  of  CaCk,  and  by  fusing 
the  two  compounds  They  have  also  been  produced  by  fusing  wolfram- 
ite with  CaCl2 

Occurrence  and  Origin — Scheehte  is  found  m  gold-quartz  veins 
and  in  veins  cutting  acid  igneous  rocks,  where  it  is  associated  with 
cassiterite,  topaz,  fluorite,  molybdenite,  wolframite  and  many  other 
metallic  compounds,  and  as  a  contact  metamorphic  product  in  altered 
limestone  intruded  by  granite  It  is  probably  m  all  cases  a  deposit 
from  hot  solutions 

Localities — It  occurs  at  Zinnwald,  Bohemia,  Altenbeig,  Saxony, 
Carrock  Fells,  Cumberland,  England,  Pitkaranta,  Finland,  in  New 
Zealand,  and  in  the  United  States  at  Monroe  and  Trumbull,  Conn  ,  in 
the  Atoha  District,  Kern  Co ,  California,  the  Mammoth  Mining  Dis- 
trict, Nevada,  in  Lake  County,  Colorado,  near  Gage,  New  Mexico, 
where  it  occurs  with  pynte  and  galena  in  a  vein  cutting  limestone, 
and  in  the  placer  gravels  at  Nome,  Alaska 

Uses  of  Tungsten  —Tungsten  is  used  puncipally  m  the  manufacture 
of  tool  steel,  electric  furnaces  and  targets  for  Ronlgen  rays  It  is 
employed  also  as  filaments  m  electric-light  bulbs,  in  the  manufacture 
of  sodium  tungstate  which  is  used  for  fireproofing  cloth,  as  a  mordant 
in  dyeing,  and  for  a  number  of  other  minor  purposes 

Production  —  Scheehte  has  been  mined  in  small  quantity  m  Idaho, 
Alaska,  California,  Nevada,  Arizona,  and  New  Mexico,  Us  a  source  of 
tungsten,  but  most  of  this  element  has  heretofore  been  produced  from 
other  compounds,  mainly  wolframite  In  1913  a  few  hundred  tons  of 
scheehte  concentrates  were  produced  m  the  Atoha  district,  California, 
and  the  Old  Hat  district,  near  Tucson,  Ariz.  At  present  (rgi6)  it  is 
being  produced  in  large  quantity  near  Bishop,  Inyo  Co.,  Cal. 

Stolzite  (PbWO4)  is  completely  isomorphous  with  wulfenite.  Its 
crystals,  which  are  pyramidal  or  short  columnar,  arc  mainly  combina- 
tions of  °oP(no),  P(in),  2P(22i)  and  oP(ooi)  Their  axial  ratio  is 
i .  i  5606 

The  mineral  is  gray,  brown,  green  or  red.  It  is  translucent  and 
has  a  white  streak  Its  hardness  is  2  75-3  and  its  sp.  gr  7.87-8.23. 
Its  refractive  indices  for  yellow  light  #re-  w  =2  2685,  €  =  2  182 

Before  the  blowpipe  it  decrepitates  and  melts  to  a  lustrous  crystal- 
line globule.  The  bead  with  microcosmic  salt  in  the  reducing  flame 


is  blue  when  cold,  in  the  oxidizing  flame  it  is  colorless  The  mineral 
is  decomposed  by  HNOs  leaving  a  yellow  residue  ol  WOs  Crystals 
have  been  made  by  fusing  sodium  tungstate  and  lead  chloride 

Its  principal  localities  are  the  tm-bearing  veins  at  Zmnwald,  Bo- 
hemia, the  copper  veins  in  Coquimbo,  Chile,  and  Southampton,  Mass  , 
where  it  is  associated  with  other  lead  compounds 

Wulfenite  (PbMoO4) 

Wulfemte  is  the  only  molybdate  of  importance  that  occurs  as  a 
mineral  Its  formula  demands  39  3  MoOs  and  60  7  PbO  Calcium 
sometimes  replaces  a  part  of  the  Pb  and  tungsten  a  part  of  the  Mo. 

Wulfemte  is  hemihedral  and  hemimorphic  (tetragonal  pyramidal 
class)  Its  crystals  are  more  frequently  tabular  than  those  of  scheelite, 
and  they  are  usually  very  thin 

The  mineral,  however,  occurs  also  m  pyramidal  and  prismatic  crys- 
tals which,  in  some  cases,  exhibit  distinct  hemunorphism  Their  axial 

Fro  147  FIG  148 

FIG  147  — Wulfemte  Crystal  with  °o  P  <*> ,  100  (a)  and  ^P  °o ,  i  o  12  (0) 

FIG    148 — Wulfenite  Crystal  with  oP,  ooi  (c),   JPoo,  102  («),   P°°,  101  (e), 

P,  in  (M)  and  JP,  113  (s) 

ratio  is  a  '  c=i  .  i  5777     The  most  common  forms  found  on  its  crys- 

r  oo  pal 
tals  are    oP(ooi),  P(ni),    —j1  (320),  fP(ii3)  and  POO(IOI)  (Fig 

147  and  148).    The  angle  in  /\1n  =  So°  22'. 

The  cleavage,  parallel  to  P,  is  very  smooth,  and  the  fracture  is  con- 
choidal  The  mineral  is  brittle  Its  hardness  is  about  3  and  specific 
gravity  about  6  8  Its  luster  is  resinous  or  adamantine,  and  its  color 
orange-yellow,  olive-green,  gray,  brown,  bright  red  or  colorless  Its 
streak  is  white  and  it  is  transparent  For  red  light,  o>=  2  402,  e=  2  304 

Before  the  blowpipe  wulfenite  decrepitates  and  fuses  readily  With 
salt  of  phosphorus  it  gives  the  molybdenum  beads  With  soda  on 
charcoal  it  yields  a  lead  globule.  When  the  powdered  mineral  is  evap- 
orated with  HC1  molybdic  oxide  is  formed  On  moistening  this  with 
water  and  adding  metallic  zinc  an  intense  blue  color  is  produced. 

Wulfenite  is  distinguished  from  tanadmtte  (p  271),  by  crystalliza- 
tion, by  the  test  for  chlorine  (vanadimte)  and  the  test  for  tungsten. 


Synthesis  — Wulf emte  crystals  have  been  produced  by  melting 
together  sodium  molybdate  and  lead  chloride 

Occurrence  and  Localities  — The  mineral  occurs  in  the  oxidized  zone 
of  veins  of  lead  ores  at  some  of  the  principal  lead  occurrences  in  Europe, 
and  in  the  United  States  near  Phoenixville,  Pennsylvania,  in  the  Organ 
Mountains,  New  Mexico,  at  the  mines  in  Yuma  County,  Arizona,  at 
the  Mammoth  Mine,  m  Pmai  County  in  the  same  State,  and  at  many 
other  of  the  lead  mines  m  the  Rocky  Mountain  states 

Uses  — Wulfenite  is  an  important  source  of  molybdenum,  but, 
because  of  the  few  uses  to  which  this  metal  is  put,  the  amount  of  wulfen- 
ite  mined  annually  is  very  small 

Wolframite  ((Fe  MnJWO*) 

Wolframite  is  the  name  given  the  isomorphous  mixtme  of  the  man- 
ganese and  iron  tungstates  that  occur  neaily  puu*  in  some  vanctics 
of  the  mineials  hubnente  and  fcrbente 

The  mixture  of  the  uon  and  manganese  molecules  is  more  common 
than  either  alone,  consequcntl}  wolframite  is  the  commonest  member  of 
the  group.  The  properties  of  all  three  mmcials,  ho\ve\cr,  arc  so  nearly 
alike  that  they  must  be  distinguished  by  chemical  analysis 

The  name  wolframite  is  usually  applied  to  mixtures  of  the  tungstates 
in  which  the  proportion  of  Fe  to  Mn  \uries  between  4  :  i  and  2  •  3,  or 
between  g  5  per  cent  and  189  per  cent  of  FeO  and  14  pci  cent  and 
4  7  per  cent  of  Mn02. 

It  has  recently  been  suggested  that  the  name  ferbente  be  limited 
to  mixtures  containing  not  more  than  20  per  cent  of  the  hubnente  mole- 
cule and  the  name  hubnerite  to  those  containing  not  more  than  20  per 
cent  of  the  ferbente  molecule  This  would  leave  the  name  wolframite 
for  mixtures  containing  more  than  20  per  cent  of  both  FcW04  and 

Analyses  of  specimens  of  hubnente  (I),  wolframite  (II  and  III) 
and  ferbente  (IV)  follow 

W03  FeO  MnO  CaO  Other  Total 

I  Ellsworth,  Nye  Co ,  Nev         7488  56  2387  .14        16  9961 

II  Sierra  Cordoba,  Argentine        7486  1345  ".°2  ,  122  10055 

III  Cabarrus  Co ,  N  C       .         7579  1980  5.35  .32       tr  101.26 

IV,  Kwnbosan,  Japan                     75  47  24  33  tr        tr  99.80 

All  members  of  the  group  crystallize  m  the  monoclinic  system 
(prismatic  class)  with  axial  ratios  as  follows 


Ferbente       a  .  b    c=  8229    i 
Wolframite  =  8300    i 

Ilubmtite  =8315     i 

8463  0=89°  38' 
8678  0=89°  38' 
8651  0=89°  38' 

The  crystals  are  pusmatic  or  cubic  in  habit  and  are  bounded  by 

ooP(uo),  ooPooJioo),  and  two  01  more  of  the  following    oP(ooi), 

oo  P  .56  (oio),  oo  P2(2io),  P  oo  (on),  -]P  66  (To2),  -  JP  66  (102),  -P(in), 

-  2?2(i2i)  and  +2P  oo  (102)  (Fig  149)    The 

angle  iioAiio  for  ferbente  =  78°  51',  for  wol 

frcimite  79°  23',  and  foi  hubnente  79°  29' 

Twins  are  fairly  common,  with  oo  P  66  (100) 

the    twinning   plane      Cleavage    is    perfect 

parallel  to  oo  P  03  (oio)     The  minerals  also 

occur  m  lamellar  and  granular  masses 

Hubnente  is   brownish  red  to  black  and 
translucent,  wolframite  is  black  and  trans- 
lucent only  on   thin   edges,  and  ferbente  is    ^'49 -Wolframite  Crys- 
,  .     .          /  *    '      .  ..  tal  with   oop,   no   (m), 

black  and  opaque.    The  streak  is  yellow  to       oopj,  2io  (/)     oopoo 

yellowish  brown  in  hubnente  and  brown  or  100(0),  —  JPoo,  102  (/), 
brownish  black  in  ferbente,  with  the  streak  P«,  011  (/),  — 2Fa,iai 
of  wolframite  between  W>  +ip55>  i°*  (y)  and 

Wolframite  is  buttle,  has  a  hardness  ot  ~~P>  IIX  W 
5-5  5,  a  specific  gravity  of  72-75,  and  a  submetallic  luster  Before 
the  blowpipe  it  fuses  to  a  globule  which  is  magnetic  Fused  with 
soda  and  niter  on  platinum  it  gives  the  bluish  green  manganate.  The 
salt  of  phosphorus  bead  is  reddish  yellow  when  hot  and  a  paler  tint 
when  cold.  In  the  reducing  flame  the  bead  becomes  dark  red  If 
the  mineral  is  treated  first  on  charcoal  with  tin  its  bead  assumes  a 
green  color  on  cooling.  The  mineral  dissolves  in  aqua  regia  with 
the  production  of  the  yellow  tungsten  trioxide  When  treated  with 
concentrated  HgSOi  and  zinc  it  yields  the  blue  tungsten  reaction 

Crystals  of  wolfiamite  are  easily  distinguished  from  crystallized 
colnmbiie  (p  293),  samarskite  (p.  295),  and  uraninite  (p  297),  by  dif- 
ferences in  crystallization  Massive  wolframite  is  distinguished  from 
massive  forms  of  the  other  three  minerals  by  its  more  perfect  cleavage 
and  by  the  reactions  with  the  beads  Uranmite,  moreover,  contains 
lead  Wolframite  is  distinguished  from  black  tourmahne  (p.  434)  by 
the  differences  m  specific  gravity, 

Occurrence  and  Ongin  — Wolframite  usually  occurs  in  veins  with  tin 
ores,  and  in  quartz  veins  with  various  sulphides,  and  in  pegmatite. 
Its  origin  is  probably  pneumatolytic. 


Localities  —Wolframite  is  found  m  all  tm-producmg  districts,  espe- 
cially at  Zmnwald,  Schneeberg  and  Freiberg,  in  Germany,  at  Ner- 
chinsk, in  Siberia,  m  Cornwall,  England,  at  Oruro,  in  Bolivia,  and  at 
various  points  in  New  South  Wales,  Australia 

In  the  United  States  it  occurs  at  Monroe,  Conn  ,  near  Mine  La 
Motte,  Missouri,  near  Lead,  South  Dakota,  where  it  impregnates  a 
sandy  dolomite,  and  at  Hill  City  in  the  same  State  in  quartz  veins, 
sometimes  containing  cassitente,  in  Boulder  Co  ,  Colorado,  in  veins 
m  granite  (ferbente),  neai  Butte,  Montana,  in  quaitz  veins  carry- 
ing silver  ores  (hubnente),  and  the  quartz-cassitcnte  veins  near  Nome 
and  on  Bonanza  Creek,  in  Alaska,  and  in  quarts  veins  at  various 
points  in  Washington,  Idaho,  California,  Nevada,  New  Mexico  and 
Arizona  At  some  of  these  localities  the  mineral  is  more  properly 

One  or  another  of  the  three  has  been  mined  in  Colorado,  Nevada, 
South  Dakota,  Montana,  Washington,  Calif oinu,  Aiizona,  and  New 
Mexico,  but  the  total  production  has  never  been  laige  Some  of  the 
ore  shipped  has  been  obtained  from  placers  along  streams  that  dram 
regions  containing  the  mineral  m  veins,  but  most  of  it  has  been  obtained 
from  vein  rock  which  is  crushed  and  concentrated 

Uses  — These  three  minerals  constitute  the  principal  source  of  tung- 
sten used  in  the  arts  The  uses  of  the  metal  are  referred  to  under 

Production — The  total  production  of  concentrates  containing  60 
per  cent  WOs  in  the  United  States  during  1913  was  1,325  tons,  valued 
at  $640,500.  Of  this,  953  tons  were  ferberite  from  Boulder  Co., 
Colorado  A  little  hubnente  was  produced  in  the  Arivica  region,  m 
southeast  California,  at  Dragoon,  Arizona,  at  Round  Mountain,  Nevada, 
and  on  Paterson  Creek,  Idaho.  In  addition,  there  were  imported 
$86,000  worth  of  tungsten-beaimg  ores  and  $143,800  worth  of  tung- 
sten metal  and  ferro-tungsten.  The  world's  production  of  tungsten  ore 
in  1912  was  9,115  tons. 


THE  phosphates  are  salts  of  phosphoric  acid,  HsPO^  the  arsenates 
of  the  corresponding  arsenic  acid,  HsAsO^  and  the  vanadates  of  the 
corresponding  vanadic  acid,  HaVC^  The  phosphates  are  by  far  the 
most  important  as  minerals  They  are  easily  distinguished  by  yielding 
phosphme,  HsP,  upon  igniting  with  metallic  magnesium  and  moistening 
the  resulting  Mg3P2  with  H20  or  HC1  (Mg3P2+6HCl=3MgCl2+ 
2PHs)  The  gas  is  recognized  by  its  disagreeable  odor  The  arsenates 
are  detected  by  the  test  for  arsenic 

The  arsenates,  phosphates  and  vanadates  form  groups  of  isomor- 
phous  compounds,  the  most  important  of  which  is  the  apatite  group 
Those  occurring  as  minerals  are  divisible  into  several  subgroups,  of 
which  the  following  six  contain  common  minerals,  viz  (i)  anhydrous 
(a)  normal  salts,  (V)  basic  salts  and  (c)  acid  salts,  and  (2)  hydrous 
(a)  normal  salts,  (b)  basic  salts  and  (c)  acid  salts 

A  number  of  the  phosphates  and  arsenates  are  of  value  commercially 
either  because  of  the  phosphorus  they  contain,  because  they  are  sources 
of  valuable  metallic  salts,  because  they  serve  to  indicate  the  presence 
of  other  valuable  compounds,  or  because  they  possess  an  ornamental 

Nearly  ail  the  phosphates  are  transparent  or  translucent  and  all  are 
nonconductors  of  electricity  or  are  very  poor  conductors, 



The  minerals  belonging  in  this  class  of  compounds  are  not  as  numer- 
ous as  the  basic  salts,  but  some  of  them  are  of  great  value  The  class 
includes  phosphates  of  yttrium,  the  alkalies,  beryllium,  cerium,  mag- 
nesium, iron  and  manganese  and  a  group  of  isomorphous  phosphates, 
arsenates  and  vanadates—  -the  apatite  group—  in  which  a  haloid  radicle 
replaces  one  of  the  hydrogen  atoms  of  the  acids  Apatite,  the  prin- 
cipal member  of  the  group,  is  an  important  source  of  phosphoric  acid 



Triphylite— (Li(Mn  Fe)PO4)— Littuophilite 

Triphylite  is  the  name  usually  applied  to  the  isomorphous  mixture 
of  LiFeP04  and  LiMnP04,  m  \vhich  the  manganese  molecule  is  present 
in  small  quantity  only  The  mixture  containing  a  large  excess  of  the 
manganese  molecule  is  called  lithiophihte 

The  pure  tnphyhte  molecule  contains  FeO=45  5  Per  cent,  LigO 
=  9  5  per  cent  and  P2Ch=45  per  cent  The  pure  lithiophilite  molecule 
consists  of  45  i  per  cent  MnO,  9  6  per  cent  Li20  and  45  3  per  cent 


Both  substances  are  orthorhombic  (bipyramidal  class),  with  an  axial 
ratio  approximating  4348  "  i  :  5265  Crystals  are  rare  and  not  well 
developed  They  are  usually  rough  prisms  bounded  by  ooFoo  (oio), 
oP(ooi),  ooP(no),  ooP2(i2o)  and  2Po6  (021)  The  minerals  usually 
occur  massive,  or  in  irregular,  rounded  crystals,  with  two  very  dis- 
tinct cleavages 

Both  minerals  are  transparent  to  translucent,  both  have  a  white 
streak,  and  both  are  vitreous  to  resinous  in  lustci  Thou  baldness  is 
about  4  5-5  and  sp  gr  about  3  5  Triphylite  is  greenish  gray  to  blue, 
and  lithiophilite  pink,  yellow  or  brown  The  refi active  indices  for 
light  brown  lithiophihte  are  a=i  676,  j3=i  679,  7=1  687,  those  for 
blue  triphyhte  are  a  trifle  higher 

When  heated  in  closed  tubes  both  compounds  are  apt  to  turn  dark 
They  fuse  at  a  low  temperature  (i  5)  and  color  the  flame  crimson  In 
the  case  of  tnphyhte  the  crimson  streak  is  bordered  by  the  green  of  iron. 
Lithiophilite  gives  the  reactions  for  Mn  Most  specimens  give  reac- 
tions for  all  these  metals — Fe,  Mn  and  Li  Both  minerals  are  soluble 

The  two  minerals  are  distinguished  from  other  compounds  by  their 
reactions  for  phosphorus  and  lithium,  and  from  each  other  by  the  reac- 
tions for  Fe  and  Mn 

Occurrence  — They  usually  occur  as  primary  constituents  of  coarse 
granite  veins  They  are  associated  with  beryl,  tourmaline  and  other 
pneumatolytic  minerals  and  with  secondary  phosphates,  which  are 
presumably  weathering  products  of  the  pnmary  phosphates 

Locahties  — Both  minerals  occur  at  a  number  of  points  associated 
with  other  lithium  compounds,  especially  spodumene  (p  378)  In  this 
country  tnphylite  has  been  found  at  Peru,  Maine,  Grafton,  Ne\\ 
Hampshire,  and  Norwich,  Massachusetts,  lithiophihte  at  Branchville, 
Connecticut,  and  at  Norway,  Maine 

Neither  of  the  minerals  possesses  a  commercial  value  at  present. 


Beryllonite  (NaBeP04) 

Beryllomte  is  a  comparatively  rare  mineral  occurring  at  only  a  few 
places  and  al\\tiys  in  crystals  or  in  crystalline  grams 

Its  composition  is  24  4  per  cent  Na^O,  19  7  per  cent  BeO  and  55  9 
per  cent  P2Cb 

Its  crystals  are  orthorhombic  (bipyramidal  class),  with  an  axial 
ratio  5724  •  i  *  540°  They  are  short  pyramidal  or  tabular  in  habit, 
often  exhibiting  a  pseudohexagonal  symmetry.  Most  crystals  are 
highly  modified  with  oP(ooi),  oo  P  60  (100),  oo  P  66  (oio),  P  66  (101) 
and  2P?(i2i),  the  principal  forms  Twins  are  common,  with  oo  P(no) 
the  twinning  plane  The  crystal  faces  are  frequently  strongly  etched 

The  mineral  is  white  to  pale  yellow  It  has  a  vitreous  luster, 
except  on  oP(ooi),  where  the  luster  is  sometimes  pearly  It  possesses 
four  cleavages,  of  which  the  most  perfect  is  parallel  to  oP(ooi).  That 
parallel  to  oo  P  60  (100)  is  distinct,  but  the  others  are  indistinct  Its 
hardness  is  5  5-6  and  its  density  2  845  Its  fracture  is  conchoidal 
Crystals  often  contain  numerous  inclusions  of  water  and  liquid  C02 
arranged  in  lines  parallel  to  L  Its  refractive  indices  for  yellow  light 
are  a=i  5520,  jS=i  5579,  7=1  5608 

Beiyllomte  decrepitates  and  fuses  in  the  blowpipe  flame  to  a  cloudy 
glass,  at  the  same  time  imparting  to  the  flame  a  yellow  color  It  is 
slowly  soluble  in  HC1,  and  gives  the  phosphorus  reaction  with  mag- 

It  is  distinguished  from  most  other  colorless  transparent  minerals 
by  the  reaction  for  phosphorus,  from  other  colorless  phosphates  by  its 
crystallization  and  the  sodium  flame  test 

Occurrence  and  Localities  — The  best  known  occurrence  of  beryllo- 
nite  m  the  United  States  is  Stoneham,  Maine,  where  it  is  found  in  the 
debris  of  a  pegmatite  dike  associated  with  apatite  (p  266),  beryl  (p.  359), 
and  other  common  constituents  of  pegmatites  It  originally  existed 
implanted  on  the  walls  of  cavities  in  the  pegmatite  and  was  apparently 
the  result  of  pneumatolytic  processes 

Use. — The  mineral  is  used  to  some  extent  as  a  gem  stone, 

Monazite  ((Ce  Di  La)PO4) 

Monazite  is  the  principal  source  of  certain  rare  earths  that  are  used 
m  manufacturing  gas  mantles  Although  it  occurs  as  small  grams  and 
crystals  m  certain  granites  it  is  found  m  commercial  quantities  only  m 
the  sands  of  streams. 


The  mineral  is  a  phosphate  of  the  metals  cerium,  lanthanum,  praseo- 
didymium  and  neodidymium  in  most  cases  combined  with  the  silicate  of 
thorium  Its  composition  may  be  represented  by  the  formula 

*((Cc  La  Di)P04)+^(ThSi04), 

in  which  the  proportion  of  the  second  constituent  varies  from  a  trace  to 
an  amount  yielding  20  per  cent  ThC>2  Since  this  is  not  constant  in 
quantity  it  is  not  to  be  regarded  as  an  essential  portion  pf  the  com- 
pound It  is  probable  that  in  monazite  we  have  to  do  with  a  solid 
solution  of  cerium  and  thorium  phosphates,  thorium  silicate  and  oxides 
of  the  rare  metals 

Monazite  is  monochnic  with  a  b  :  c=  9693  '  i  :  9255  and  0= 
76°  20'  Crystals  are  usually  prismatic  with  the  pinacoids  oo  P  56  (100), 
ooPob(oio),  the  prism  ooP(no),  the  two  domes  — POO(IOI)  and 
+P66(ioY)  and  the  pyramids  -P(in)  and  +P(nT)  They  are 
often  flattened  parallel  to  the  orthopmacoid 
(Fig  150)  The  angle  1 10  A  iTo= 86°  34' 

Their  cleavage  is  perfect  parallel  to   oP 
The  color  of  the  mineral  is  gray,  yellow,  red- 
dish, brown  or  green     It  is  usually  transpar- 
ent or  translucent  and  sometimes  opaque     It 
is  brittle,  has  a  white  streak,  and  a  resmous 
luster     Its  hardness  is  5-5  5  and  its  sp  gr 
FIG.  150— Monazite  Ciys-  4  7-5  3,  varying  with  the  proportion  of  thorium 
tal  with  oo  POO,  ioo  (a),          nt     The   refractive    indices   for   yellow 

00  P.      110      (0Z),        00  ?2,     ,      ,  0  0 

»o  (,),  oo  P  S,  oxo  (*),   hSht  are    a=I  7938,  7  -  t  8452. 
-Poo,  ioi  (w),  +Pco,        The  mineral  is  infusible     Before  the  blow- 
iol  (x)  and  P,  nI  (»)       pipe  it  turns  gray,  and  when  moistened  with 
H2S04  it  colors  the  flame  bluish  green     It  is 

difficultly  soluble  in  HC1  and  HNOs  Most  specimens  are  strongly 

Synthesis  — Crystals  of  monazite  have  not  been  prepared,  but  crys- 
tals of  cerium  phosphate  similar  to  those  of  monazite  have  been  made 
by  heating  to  redness  a  mixture  of  cerium  phosphate  and  cerium  chloride 
Occurrence  and  Ongvn  — Monazite  occurs  as  the  constituent  of  cer- 
tain granites  and  granitic  schists  in  small  crystals  scattered  among  the 
other  components  In  this  form  it  is  a  separation  from  the  granitic 
magma  When  the  granites  are  broken  down  to  sand  by  weathering 
the  monazite  is  freed  and  because  of  its  specific  gravity  it  concentrates 
in  stream  channels 

Localities  — Although  the  mineral  is  fairly  widespread  in  the  rocks, 


it  is  concentrated  into  commercial  deposits  at  only  a  few  places.  The 
most  important  of  these  are  in  southeastern  Brazil,  in  Norway,  and  in  a 
belt  20  to  30  miles  wide  and  150  miles  long  extending  along  the  east  side 
of  the  Appalachian  Mountains  from  North  Carolina  into  South  Carolina 

The  mineral  has  also  been  reported  from  many  points  in  ten  coun- 
ties in  Idaho  Near  Centerville  it  may  be  m  sufficient  quantity  to  be 
of  commercial  importance 

Preparation — Monazitg  is  separated  from  the  valueless  sand  in 
which  it  is  found,  by  washing,  and  the  residues  thus  resulting  are  further 
concentrated  by  a  magnetic  process  The  commercial  concentrates 
produced  in  this  way  usually  contain  from  3  to  9  per  cent  ThCfe,  and 
their  price  varies  accordingly 

Production  and  Uses  — Monazite  is  the  chief  source  of  thorium  oxide 
used  in  the  manufacture  of  incandescent  gas  mantles  Formerly  it  was 
produced  in  large  quantity  in  the  Carohnas,  the  production  m  1909 
amounting  to  542,000  Ib ,  valued  at  $65,032,  and  in  1905  to 
1,352,418  Ib ,  valued  at  $163,908.  All  of  this  was  manufactured  into 
the  nitrate  of  thorium  in  this  country  and  the  amount  made  was 
not  sufficient  to  meet  the  domestic  demand.  Consequently,  large  quan- 
tities of  the  nitrate  were  imported  In  1910-11  mining  of  the  mineral 
m  the  Carohnas  ceased  and  all  the  monazite  needed  has  been  imported 
since  then  The  imports  of  thorium  nitrate  for  1912  were  117,485  Ib  , 
valued  at  $225,386  and  of  monazite,  an  amount  valued  at  $47,334 

Xenotime  (YPO4) 

Xenotime,  though  essentially  an  yttrium  phosphate,  usually  contains 
erbium  and  in  some  cases  cerium. 
It  occurs  in  tetragonal  crystals 
and  m  rolled  grains  Its  axid 
ratio  is  i  6177  and  ^e  angle 
in  A  ill  =*  55°  30'  Its  crystals 
are  octahedral  or  prismatic  and 
are  bounded  by  oo  P(iio),P(m), 
and  in  some  cases  by  oo  P  oo  (100) 
and  2P  oo  (201)  (Fig  151)  Their 
cleavage  is  perfect  parallel  to  FIG  151 -Xenotime  Crystals  with  OOP  no 

•n/        \      onT  iv  W»  P    II3C  W»  ^   ^P00*  I°°  W 

ooP(no)    The  mineral  is  brown,       v  " 

pink,  gray  or  yellow  Its  streak  is  a  pale  shade  of  the  same  color. 
It  is  opaque  and  brittle  Its  luster  is  vitreous  or  resinous,  its  hardness 
4-5  and  specific  gravity  45  Its  indices  of  refraction  are:  e=i8i, 
w=i  72 


Xenotime  is  infusible,  insoluble  in  acids  and  with  difficulty  soluble 
in  molten  microcosmic  salt  It  is  distinguished  from  zircon  by  its 
cleavage  and  inferior  hardness 

A  variety  of  xenotime  containing  a  small  percentage  of  sulphates  is 
known  as  hussakite 

The  mineral  occurs  in  pegmatite  veins,  in  granites  and  in  the  sands 
of  streams  It  is  found  in  pegmatite  veins  at  Hittero,  Moss,  and  other 
places  in  Norway,  at  Ytterby,  Sweden,  in  the  granites  of  Mmas  Geraes, 
Brazil,  and  m  the  gold  washings  at  Clarksville,  Georgia,  and  many  places 
in  North  Carolina,  and  in  pegmatite  veins  in  Alexander  County  in  the 
same  State 


The  apatite  group  consists  of  a  number  of  phosphates,  arsenates  and 
vanadates  in  which  fluorine  or  chlorine  takes  the  place  of  the  hydroxyl 
in  basic  compounds  Thus,  fluorapatite  is  Ca4(CaF)(P04)s  and  chlor- 
apatite  Ca^CaGXPOOs  The  group  contains  a  number  of  important 
minerals,  of  which  apatite  is  by  far  the  most  valuable  These  minerals 
are  isomorphous,  all  crystallizing  in  the  hemihedral  division  of  the  hex- 
agonal system  (hexagonal  bipyramidal  class)  The  names,  composi- 
tions and  axial  ratios  of  the  most  important  are  as  follows 

Fluorapatite  Ca4(CaF)(PC>4)3  a    c=i      7346 

Chlorapatite  Ca^CaClXPCWs  a    c**i:   7346+ 

PyromorpTtite  Pb4(PbCl)(P04)3  a.c=i     7293 

Mimetite  Pb4(PbCl)(As04)3  0  .  e-i  :   7315 

Vanadmite  Pb4(PbCl)(V04)s  a:c-i:  7122 

Apatite  (Ca4(Ca(F  C1))(PO4)3) 

Although  fluorapatite  and  chlorapatite  are  distinct  compounds  with 
slightly  different  properties,  nevertheless,  because  of  the  difficulty  of 
discriminating  between  them  without  analyses,  the  name  apatite  is 
commonly  applied  to  both  This  is  justified  because  of  the  fact  that  the 
two  compounds  are  completely  isomorphous,  and  the  mineral  as  it 
usually  occurs  is  a  iruxture,  of  both  The  ideal  molecules  comprising 
the  two  varieties  of  apatite  have  the  following  compositions 

Fluorapatite    CaO=5S5,  F=3  8,  P205=42  3 
Chlorapatite    CaO=53  8,  Cl=6  8,  P20s==4i  o 

Apatite  is  found  in  well  defined  crystals,  sometimes  very  large 
These  have  a  holohedral  habit,  but  etch  figures  on  their  basal  planes 


reveal  the  grade  of  symmetry  of  pyramidal  hemihednsm  The  min- 
eral occurs  also  massive,  in  granular  and  fibrous  aggregates  and  less 
commonly  in  globular  forms  and  as  crusts 

The  crystals  are  usually  columnar  or  tabular,  with  the  hexagonal 
prism  or  pyramid  well  developed  Although  in  some  cases  highly 
modified,  most  crystals  contain  only  the  oo  P(iolo),  P(ioTi)  and  oP(oooi) 
planes  prominent,  though  £P(iol2)  and  2P2(ii2i)  are  not  uncommon  as 
small  faces  (Figs  152  and  153)  Their  cleavage  is  indistinct,  and  their 
fracture  often  conchoidal 

Apatite  may  possess  almost  any  color  In  a  few  cases  the  mineral  is 
colorless  or  amethystine  and  transparent,  but  in  most  cases  it  is  trans- 
lucent or  opaque  and  white,  green,  bluish,  brown  or  red  Its  streak  is 

FIG  152.  FIG  153 

FIG   152 — Apatite  Crystals  with  cop,  ioYo  (w),  P,  loTi  (r),   oP,  oooi  (c),   JP, 

iol2  (r)  and  oop2,  1120  (a) 

FIG  153  — Apatite  Crystal  with  m,  %,  r  and  c  as  in  Fig  152  and  2?,  2021  (y),  4P|, 
1341  (»),  3?J,  1231  GU),   2P2,  nil  (5),  P2,  1122  (B)  and  oo?},  1230  (A) 

white  and  its  luster  vitreous  to  resinous  Its  hardness  is  4  5-5  and  sp 
gr  between  3  09  and  3  39  The  refractive  indices  of  fluorapatite  for 
yellow  light  are  6>=i  6335,  €=1.6316  and  of  chlorapatite,  co=i  6667 
Many  specimens  are  distinctly  phosphorescent  Nearly  all  fluoresce  in 
yellowish  green  tints,  and  all  are  thermo-electric 

Apatite  fuses  with  difficulty,  tinging  the  flame  reddish  yellow  The 
chlorapatite  melts  at  1530°  and  the  fluorine  variety  at  1650°  When 
moistened  with  H2S04  all  varieties  color  the  flame  pale  bluish  green, 
due  to  the  phosphoric  acid  Specimens  containing  chlorine  give  the 
brilliant  blue  color  to  the  flame  when  fused  in  a  bead  of  microcosmic 
salt  that  has  been  saturated  with  copper  oxide  Specimens  containing 
fluorine  etch  glass  when  fused  with  this  salt  in  an  open  glass  tube 
The  mineral  also  yields  phosphme  when  ignited  with  magnesium,  and 
it  dissolves  in  HC1  and  HNOs 


Apatite  is  much  softer  than  beryl  (p  359)>  which  it  closely  resembles 
in  appearance  It  is  distinguished  from  calcite  by  lack  of  effervescence 
•with  acids  and  from  other  compounds  by  the  phosphorus  reaction 

The  vaneties  of  the  mineral  recognized  by  distinct  names  are 

Ordinary  apatite^  crystals  or  granular  masses 

Manganapatite,  in  which  manganese  partly  replaces  the  Ca  of  ordi- 
nary apatite^  This  is  dark  bluish  green 

Fibrous,  conci  etionary  apatite     Known  also  as  phosphorite 

Osteohte     The  earthy  variety 

Phosphate  rock.  A  mixture  of  apatite,  phosphorite,  several  hydrous 
carbonates  and  phosphates  of  calcium,  and  fragments  of  bone  and 
teeth  It  is  more  properly  a  rock  with  a  brecciated  and  concretionary 
structure  The  composition  of  typical  deposits  is  represented  by  the 
following  analysis  of  hard  rock  phosphate  from  South  Carolina 

CaO      P205    C02  Fe203  Al20s    MgO  Insol   Undet     H20     Moist 
50  08      38  84     65       96      3  07        30      49      2  46      2  96         07 

Guano  is  a  mixture  of  various  phosphates,  both  hydrous  and  an- 
hydrous, calcite  and  a  number  of  other  compounds  It  is  rather  a  rock 
than  a  mineral,  as  it  has  no  definite  composition 

Syntheses  —Crystals  of  fluorapatite  have  been  made  by  fusing 
sodium  phosphate  with  CaF2  and  by  heating  calcium  phosphate  with  a 
mixture  of  KF  and  KC1 

Origin — The  crystallized  apatite  was  formed  by  direct  separation 
from  igneous  rock  magmas  and  by  pneumatolytic  action  upon  limestone 
The  phosphorite  variety  and  the  phosphate  in  phosphate  rock  were 
probably  produced  by  the  solution  of  calcium  phosphate  and  its  later 
deposition  from  solution— the  original  phosphate  having  been  furnished 
in  many  cases  by  the  shells  of  mollusca,  and  by  the  action  of  phosphoric 
acid  produced  by  the  decay  of  organisms  upon  limestone  In  many 
cases  phosphorite  accumulated  as  a  residual  deposit  in  consequence  of 
the  solution  of  the  calcite  and  dolomite  from  phosphatic  limestone, 
leaving  the  less  soluble  phosphate  as  a  mantle  on  the  surface. 

Occurrence  — The  mineral  occurs  in  microscopic  crystals  as  a  com- 
ponent of  many  rocks,  as  large  crystals  in  metamorphosed  limestones, 
as  a  component  of  many  coarse-grained  veins,  especially  those  composed 
of  coarse  granite  and  those  in  which  cassiterite,  magnetite,  tourmaline, 
and  other  pneumatolytic  minerals  are  found  At  a  number  of  places 
aggregates  of  apatite  and  magnetite  or  ilmemte  occur  in  such  large 
masses  as  to  be  worthy  of  being  called  rocks  An  impure  apatite  in 
concretionary  and  fibrous  forms  also  occurs  in  thin  beds  covering  large 


areas.  It  is  often  mixed  with  other  phosphates,  with  the  bones  and 
teeth  of  animals  and  with  other  impurities  This  is  the  well  known 
phosphate  rock  or  phosphonte 

Localities  — Crystallized  apatite  is  so  widely  spread  that  it  is  useless 
to  mention  its  occurrences  It  is  mined  at  Kragero  and  near  Bamle, 
in  Norway,  at  various  points  in  Ottawa  County  in  Quebec,  and  in 
Frontenac,  Lanark  and  Leeds  Counties  in  Ontario,  and  at  Mineville, 
New  York  Rock  phosphate  is  found  in  extensive  beds  on  the  west 
side  of  the  peninsula  of  Florida,  in  South  Carolina,  North  Carolina, 
Alabama,  Tennessee,  Wyoming,  Idaho,  Utah  and  Arkansas  A  mixture 
of  apatite  and  ilmemte  (nelsomte),  occurs  as  dikes  in  Nelson  and 
Roanoke  Counties,  Virginia 

Uses  — The  principal  use  of  apatite  and  phosphate  rock  is  in  the 
manufacture  of  fertilizers  The  rock  (or  crushed  apatite)  is  treated 
with  H2S04  to  make  an  acid  phosphate  which  is  soluble  in  water  Am- 
monia or  potash,  or  both,  are  added  to  the  mass  and  the  compound  is 
sold  as  a  superphosphate.  The  purest  varieties  are  treated  with  H2S04 
in  sufficient  quantity  to  entirely  decompose  them,  CaSO*  and  HsPO* 
being  formed  The  latter  is  drawn  off  and  mixed  with  additional  high- 
grade  rock  and  the  mixture  is  known  as  concentrated  phosphate  Super- 
phosphates are  manufactured  in  large  quantities  in  the  United  States 
and  the  concentrated  phosphates  in  Europe  Unfortunately,  for  the 
latter  use  the  best  grades  of  apatite  or  rock  phosphate  are  required,  and 
consequently  the  best  grades  of  rock  produced  in  the  United  States  are 
exported  and  thus  lost  to  American  farmers 

Production  —The  world's  production  of  apatite  and  phosphate  rock 
during  1912  was  as  follows* 

United  States  3,020,905  tons,  valued  at  $11,675,774 

Tunis  2,050,200  tons,  valued  at  7,500,000 

Christmas  Island  159459  tons,  valued  at  2,024,036 

France  313*151  tons,  valued  at  1,169,400 

Algeria  207,111  tons,  valued  at  759455 

Belgium  203,1 10  tons,  valued  at  316,703 

Other  countries  65,000  tons,  valued  at  280,000 

For  the  United  States  production  of  1912  the  statistics  are: 

Florida 2,407,000  tons,  valued  at  $9,461,000 

Tennessee  423,300  tons,  valued  at    1,640,500 

South  Carolina  131,500  tons,  valued  at      524,700 

Other  States  11,600  tons,  valued  at        49»200 


The  total  production  was  3,020,905  tons,  valued  at  $11,675,77400, 
of  which  1,206,520  tons,  valued  at  $8,996,45600  were  exported  Par- 
tially offsetting  this,  there  were  imported  guano,  apatite  and  other  phos- 
phates to  the  value  of  about  $2,000  ooo, 

Pyromorphite  (Pb4(PbCl)(PO4)3) 

In  composition  pyromorphite  is  PbO,  82  2  per  cent,  PoO«i,  15  7  per 
cent  and  Cl,  2  6  per  cent,  but  there  are  usually  present  also  CaO  and 

The  mineral  is  completely  isomorphous  \\ith  apatite  Its  crystals 
are  smaller  and  simpler  than  those  of  apatite,  but  they  have  the  same 
habit  Their  axial  ratio  is  a  c=i  '  7293  This  increases  to  i  :  7354 
in  varieties  containing  calcium 

Crystals  are  often  rounded  into  barrel-shaped  forms,  and  frequently 
are  mere  skeletons  Tapering  groups  of  slender  crystals  in  parallel 
growths  are  also  common  Their  cleavage  is  parallel  to  the  &o  P(no) 
faces,  and  their  fracture  is  feebly  conchoidal.  The  mineral  also  occurs 
in  globular,  granular  and  fibrous  masses 

Pyromorphite  is  translucent  It  is  brittle,  has  a  hardness  of  3  5-4 
and  a  density  of  about  7  Its  luster  is  resinous  and  color  usually  green, 
yellow,  brown  or  orange  Some  varieties  are  gray  or  milk-white  Its 
streak  is  white  Its  refractive  indices  foi  yellow  light  are:  o>=2  0614, 
6=2  0494  The  mineral  is  distinctly  thermo-electric. 

When  heated  m  the  closed  tube  pyromorphite  gives  a  white  subli- 
mate of  lead  chloride  It  fuses  easily,  coloring  the  flame  bluish  green 
When  heated  on  charcoal  it  melts  to  a  globule,  which  crystallizes  on 
cooling  and  yields  a  coating  which  is  yellow  (PbO)  near  the  assay  and 
white  (PbCk),  at  a  greater  distance  from  it.  When  fused  with  Na2COs 
on  charcoal  a  globule  of  lead  results  The  mineral  also  gives  the  Cl  and 
P  reactions  The  mineral  is  soluble  in  HNOa 

Pyromorphite  is  recognized  by  its  form,  high  specific  gravity  and  its 
action  when  heated  on  charcoal 

Synthesis.  —  Crystals  have  been  obtained  by  fusing  sodium  phosphate 
with  PbCk. 

Occurrence—  The  mineral  occurs  principally  m  veins  with  other  lead 
ores,  especially  in  the  zone  of  weathering  It  also  exists  in  pseudomorphs 
after  galena. 

Localities  —  It  is  found  in  all  lead-producing  regions,  especially  in 
the  upper  portions  of  veins  It  occurs  m  particularly  good  specimens 
at  Pribram,  Bohemia,  at  Ems,  m  Nassau,  in  Cornwall,  Devon,  Derby- 


shire  and  Cumberland,  England,  at  Phoemwille,  Pennsylvania,  and 
at  various  other  points  in  the  Appalachian  region 

Vies—  Pyromorphite  alone  possesses  no  commercial  value,  but  it 
is  mined  with  other  compounds  of  lead  as  an  ore  of  this  metal 

Munetite  (Pb4(PbCl)(AsO4)3) 

Mimetite,  or  mimetesite,  resembles  pyromorphite  in  its  crystals  and 
general  appearance,  and  many  of  its  properties  Its  color,  however,  is 
lighter  and  its  density  slightly  greater  It  occurs  in  crystals,  m  fila- 
ments, and  in  concretionary  masses  and  crusts  Its  axial  ratio  Is 
i  7315  and  its  refractive  indices  for  yellow  light  are  w=2  1443,  e 
=  2  1286 

The  formula  for  mimetite  demands  74  9  per  cent  PbO,  23  2  per  cent 
AS205  and  2  4  Cl  Usually  a  portion  of  the  lead  is  replaced  by  CaO  and 
a  portion  of  the  As  by  P 

Mimetite  fuses  more  easily  than  pyromorphite  It  differs  from  this 
mineral  in  yielding  arsenical  fumes  when  heated  on  charcoal  More- 
over, when  heated  in  a  closed  tube  with  a  fragment  of  charcoal  it  coats 
the  walls  of  the  tube  with  metallic  arsenic 

Occurrence  and  Localities — It  occurs  with  other  lead  minerals  in 
veins,  usually  coating  them  either  as  crusts  or  as  a  series  of  small  crys- 
tals It  is  found  at  Phoenix ville,  Pennsylvania,  m  Cornwall,  England, 
at  Johanngeorgenstadt,  in  Germany,  at  Nerchinsk,  Siberia,  at  Lang- 
ban,  in  Sweden,  and  at  a  number  of  other  places  It  is,  however,  not 
as  common  as  the  corresponding  phosphorus  compound 

Uses  — It  is  mined  with  other  compounds  as  an  ore  of  lead. 

Vanadiaite  (Pb4(PbCl)(VO4))3 

Vanadmite  is  the  most  widely  distributed  of  all  the  vanadium  min- 
erals It  usually  occurs  in  small  bright  red  prismatic  crystals  implanted 
on  other  minerals,  or  on  the  walls  of  crevices  in  rocks  It  is  one  of  the 
sources  of  vanadium 

Its  theoretical  composition  is  as  follows  PbO =78  7  per  cent, 
¥205=19  4  per  cent  and  Cl=2  5  per  cent,  but  phosphorus  and  arsenic 
are  often  also  present  When  arsenic  and  vanadium  are  present  m 
nearly  equal  quantities  the  mineral  is  known  as  endhckite. 

Its  crystals  are  hexagonal  prisms  and  pyramids  bounded  by 
ooP(ioTo),  oP(oooi),  ooP2(u5o\  P(ioTi)  and  other  forms,  with  an 
axial  ratio  i  :  .7122  (Fig  154).  Often  the  crystals  have  hollow  faces 



(Fig  IS5)  Frequently  they  are  grouped  into  pyramids  like  those  of 
pyromorphite  The  mineral  occurs  also  m  globules  and  crusts 

Vanadmite  is  brittle,  has  a  hardness  of  about  3  and  a  specific  gravity 
of  about  7  Its  fracture  is  conchoidal  Its  luster  is  adamantine  or 
resinous  and  its  color  ruby  red,  brownish  yellow  or  reddish  brown 
Its  streak  is  white  or  light  yellow  The  mineral  is  translucent 
or  opaque  Its  refractive  indices  for  yellow  light  are  ^=2354, 
€=  2  299 

In  the  closed  tube  vanadimte  decrepitates  It  fuses  easily  on  char- 
coal to  a  black  lustrous  mass  which  is  reduced  on  being  further  heated 
in  the  reducing  flame  to  a  globule  of  lead  A  white  sublimate  of  PbCk 
also  coats  the  charcoal  The  mineral,  moreover,  gives  the  flame  test 

FIG.  154 

FIG  154  FIG  155 

—Vanadimte  Crystal  with  <x>p,  loTo  (m),  oP,  oooi  (c),  P,  icTi  (#),  and 

FIG  155  —  Skeleton  Crystal  of  Vanadimte 

for  chlorine  with  copper  After  complete  oxidation  of  the  lead  by  heat- 
ing in  the  oxidizing  flame  on  charcoal  the  residue  gives  an  emerald-green 
bead  in  the  reducing  flame  with  microcosmic  salt  and  this  turns  to  a 
light  yellow  m  the  oxidizing  flame  The  mineral  is  soluble  m  hydro- 
chloric acid.  If  to  the  solution  a  little  hydrogen  peroxide  is  added  it 
will  turn  brown  The  addition  of  metallic  tin  to  this  will  cause  it  to 
turn  blue,  green  and  lavender  in  succession,  in  consequence  of  the  reduc- 
tion of  the  vanadium  compounds 

Vanadimte  is  easily  distinguished  from  most  other  minerals  by  its 
color,  It  is  distinguished  from  other  compounds  of  the  same  color  by 
its  crystallization  and  by  the  reactions  for  vanadium 

Occurrence  —  Vanadmlte  occurs  principally  in  regions  of  volcanic 
rocks  It  is  probably  a  result  of  pneumatolytic  processes 

Localities  —Crystals  are  found  at  Zimapan,  Mexico,  Wanlockhead, 


England,  Undenas,  Sweden,  in  the  Sierra  de  Cordoba,  Argentine,  and  in 
the  mining  districts  of  Arizona  and  New  Mexico 

Uses — Vanadmite  is  an  important  source  of  vanadium,  which  is 
employed  m  the  manufacture  of  certain  grades  of  steel  and  bronze 
Its  compounds  are,  moreover,  used  as  pigments  and  mordants  Most 
of  the  vanadium  compounds  produced  in  this  country  are  obtained  from 
other  vanadium  minerals,  among  them  patromte — a  mixture,  of  which 
the  principal  component  is  a  sulphide  (VS.*) — and  carnotite  (p  290), 
but  vanadmite  has  been  used  abroad  and  also  to  a  small  extent  in  the 
United  States 


This  group,  in  chemical  composition,  is  analogous  to  the  apatite 
group  It  includes  a  number  of  phosphates  and  arsenates  containing  a 
fluoride  radical  The  group  is  monochmc  (prismatic  class),  with  an 
axial  ratio  which  is  approximately  19.1  15,  with  18=71°  50'  None 
of  its  members  are  important  The  two  most  common  ones  are  wag- 
nente  (Mg(MgF)PO4),  and  tnphte  (Fe  Mn)  ((Fe  Mn)F)P04 

Wagnerite  occurs  in  massive  forms  and  in  large  rough  crystals,  with 
imperfect  cleavages  parallel  to  oo  P  55  (100)  and  oo  P(no)  Its  crystals 
have  an  axial  ratio  of  i  9145  •  i  .  i  5059  \vith  £=71°  53'  They  are 
often  very  complex  The  mineral  is  bnttle  Its  fracture  is  uneven 
Its  hardness  is  5  5  and  density  3  09  Its  color  is  yellow,  gray,  pink  or 
green  It  is  vitreous,  translucent  and  has  a  white  streak  Its  refractive 
indices  are  a=i  569,  £=i  570,  7  =  1  582  It  fuses  to  a  greenish  gray 
glass  and  gives  the  usual  reactions  for  fluorine  and  phosphoric  acid  It 
is  soluble  in  HC1  and  HNOa,  and  heated  with  HgSOi  it  yields  hydro- 
fluoric acid  It  occurs  in  good  crystals  near  Werfen,  Austria,  and  in 
coarse  crystals  near  Bamle,  Norway. 

Triplite  is  an  isomorphous  mixture  of  Fe(FeF)PO4  and  Mn(MnF)P04 
It  usually  occurs  massive,  but  is  found  in  a  few  places  in  rough  crystals 
The  mineral  is  dark  brown  or  nearly  black,  is  translucent  to  opaque, 
and  has  a  yellowish  gra}'  or  brown  streak  It  possesses  two  unequal 
cleavages  perpendicular  to  one  another  and  a  weakly  conchoidal  frac- 
ture Its  hardness  is  4-5  5  and  specific  gravity  about  3  9  Its  luster  is 
resinous.  Its  intermediate  refractive  index  is  i  660 

Before  the  blowpipe  tnplite  fuses  easily  (i  5)  to  a  black  magnetic 
globule  It  reacts  for  Mn,  Fe,  F,  and  PaOs  It  is  soluble  in  HC1  and 
evolves  hydrofluoric  acid  with  H2S04  It  is  found  in  coarse  granite 


veins  at  Limoges,  France,  Helsingfors,  Finland,  Stoneham,  Maine, 
and  Branchville,  Connecticut  In  all  of  its  occurrences  it  appears  to 
be  pneumatolytic 


The  basic  phosphates  are  those  in  which  there  is  more  metal  present 
than  sufficient  to  replace  the  three  hydrogen  atoms  in  the  normal  acid, 
HsP04     This  is  due  to  the  replacement  of  one  or  more  of  the  hydrogen 
atoms  by  a  group  of  atoms  consisting  of  a  metal  and  hydroxyl  (OH) 
All  yield  water  when  heated  in  the  closed  tube 

The  principal  basic  phosphates  are  amblygonite,  a  source  of  lithium 
compounds,  dufremte  and  lazidite,  neither  of  which  is  of  economic  im- 
portance, and  hbethemte,  a  copper  compound  which  occurs  in  compara- 
tively small  quantities  with  other  copper  ores,  and  is  mined  with 

Ohvenite  is  a  basic  copper  arsenate  corresponding  to  the  phosphate 

Amblygonite  (Li(Al(F  OH))PO4) 

Amblygomte  is  an  isomorphous  mixture  of  the  two  compounds 
(AlF)LiP04  and  (AlOH)LiPO-i  It  is  an  important  source  of  lithium 

The  composition  of  the  fluorine  molecule  is  Al20s=344  per  cent, 
Li02=io  i  per  cent  and  P20s=47  9  per  cent,  making  a  total  of  105  3 
per  cent  from  which  deducting  5  3  per  cent  (0=  sF),  leaves  100  Nearly 
always  a  portion  of  the  F  is  replaced  by  OH  and  a  part  of  the  Li 
by  Na  The  pure  Na(A10H)P04  is  known  as  fremontite,  and  the  pure 
Li(A10H)PO4  as  montebrmte 

The  analysis  of  a  specimen  from  Pala,  California,  gave: 

Pa06        AlsOs      PesOs    MnO     MgO       LiaO      NaaO      H8O  0-P    Total 

4883        3370          12         09  31         988          14       595        229*10131-96     -     100  45 

The  mineral  forms  large,  ill-defined  triclmic  crystals  (Fig  156),  and 
compact  masses  with  a  columnar  cleavage  Crystals  are  very  rare,  and 
are  poorly  developed  Their  axial  ratio  is  .7334  :  i  :  7633.  The 
cleavage  pieces  often  show  polysynthetic  twinning  lamellae  parallel  to 

The  cleavage  of  the  mineral  is  perfect  parallel  to  oP(ooi)  Its 
fracture  is  uneven  It  is  brittle,  has  a  hardness  of  6  and  a  density  of 
3  03,  Its  color  is  white,  gray,  or  a  very  light  tint  of  blue,  pink  or 
yellow  Its  luster  is  vitreous,  except  on  oP  where  it  is  pearly.  '  Its 


FIG  156 — Amblygoiute 
Crystal  with  ooPoo, 
100  (a),  oP,  ooi  (c), 
oo ]P,  no  (A/),  °oP', 
no  (m)y  w'P's,  120 

(=),     /P/J5,    ioi     (K) 

and  2'P  oo ,  02 1  (e) 

streak  is  white  and  it  is  translucent     Its  refractive  indices  for  yellow 
light  are   a=i  579,  /3=i  593,  7=1  597 

In  the  closed  tube  at  high  temperature  it  yields  water  which  reacts 
acid  and  corrodes  glass  It  fuses  easily  to  an 
opaque  white  enamel  It  colors  the  flame  red 
with  a  slight  fringe  of  green  When  moistened 
with  H2S04  it  tinges  the  flame  bluish  green 
When  finely  powdered  it  dissolves  readily  in 
H2SO4  and  with  difficulty  in  HC1 

Amblygomte  resembles  in  appearance  many 
other  minerals,  especially  spodumene  (p  378), 
and  some  forms  of  bante,  feldspar,  dolomite,  etc 
From  spodumene  it  is  distinguished  by  the  phos- 
phorus reaction  and  the  acid  water,  from  the 
others  by  its  easy  fusibility 

Occurrence  —  Amblygomte  is  found  in  granite 
and  in  pegmatite  veins  associated  with  other 
lithium  compounds,  tourmaline,  cassitente  and 
other  minerals  of  pneumatolytic  origin  In  all  cases  it  also  is  probably 
a  result  of  pneumatolytic  action  associated  with  the  last  phases  of  granite 

Localities  —  The  mineral  occurs  near  Pemg,  in  Saxony,  at  Arendal, 
in  Norway,  at  Montebras,  France,  at  Hebron,  Paris  and  Peru,  Maine, 
at  Branchville,  Conn  ,  at  Pala,  m  California,  and  near  Keystone,  in 
the  Black  Hills,  South  Dakota 

Uses  and  Production  —  The  mineral  is  the  pnncipal  source  of  lithium 
compounds  in  the  United  States.  It  is  used  in  the  manufacture  of 
LiCOa,  which  is  employed  as  a  medicine,  in  making  mineral  waters,  in 
photography  and  in  pyrotechnics 

It  has  been  mined  m  South  Dakota  and  in  California  to  the  extent 
of  a  couple  of  thousand  tons,  valued  perhaps  at  $20,000. 

Dufrenite  QfeaCOHJsPO*) 

Dufreiute,  or  kraunte,  is  a  basic  iron  phosphate  containing  62  per 
cent  FegOs,  27  5  per  cent  P20s  and  10  5  per  cent  water  It  may  be 
regarded  as  a  normal  phosphate  in  which  one  H  atom  of  HsP04  has  been 
replaced  by  the  Fe(OH)2  group  and  two  by  the  group  Fe(OH),  thus 

It  forms  small  orthorhombic  crystals  with  a  cubic  habit  that  are  rare 
Their  axial  ratio  is  .3734  •  i  •  .4262.    It  usually  occurs  massive,  in 



nodules,  or  in  fibrous  radiating  aggregates  The  same  substance  is 
belie\  ed  to  occur  also  in  the  colloidal  condition  under  the  name  ddvauute 

The  color  of  dufremte  varies  from  leek-green  to  dark  green,  which 
alters  on  exposure  to  yellow  and  brown  It  is  translucent  to  opaque, 
has  a  light  green  streak  and  is  strongly  pleochroic  Its  hardness  is 
3  5-4  and  specific  gravity  about  3  3 

In  the  closed  tube  it  yields  water  and  whitens  It  fuses  easily,  color- 
ing the  flame  bluish  green  and  yielding  a  magnetic  globule  It  is  sol- 
uble in  HC1  and  in  dilute  H2S04 

It  is  recognized  by  its  color  and  the  presence  in  it  of  water,  phos- 
phorus and  iron 

Localities  and  Origin — The  mineral  has  been  observed  at  several 
points  in  Europe,  at  Allentown,  New  Jersey,  and  in  Rockbridge  County, 
Virginia  It  is  thought  to  be  produced  by  the  weathering  of  other  fer- 
ruginous phosphates 

LazuHte  ((Mg  Fe)(AlOH)2(PO4)2) 

Lazulite  is  essentially  an  isomorphous  mixture  of  the  two  com- 
pounds Mg(A10H)2(P04)2  and  Fe(AlOH)2(POi)2  There  is  also  fre- 
quently present  m  it  a  little  calcium 
When  the  proportion  of  the  two 
molecules  present  is  as  2  .  i  the  com- 
position becomes  FeO =  77,  MgO 
=  85,  A1203  =  32  6,  P205  =  4S  4  and 

The  mineral  occurs  m  blue  pyram- 
idal  crystals    that    are    monoclimc 
(prismatic  class),  with  the  axial  ratio 
=  9750  •  i  •  i  6483  and  0=89°  14' 
The  predominant  forms  are  +P(nT), 
FIG   157— Lazulite  Crystals     A  with    —  P(lli)  and— P  56  (ioi)(Flg  157-4) 
-P,  in  (p)  H-P,  nl  (e)  and  P  65 ,  xhe  angle  in  A  if  i  =  79°  40'     Twins 

ioi  (/)  B  is  the  same  combination 
twinned  about  oo  p  oo  (100)  with  oP 
(ooi)  the  composition  face 

are  not  common     Those  most  fre- 
quently found  are  twinned  about  c 
as  the  twinning   axis    (Fig    1576) 
It  is  found  also  massive  and  in  granular  aggregates 

The  cleavage  of  lazuhte  is  not  distinct  Its  fracture  is  uneven  It 
is  brittle,  has  a  vitreous  luster,  is  translucent  or  opaque,  has  an  azure 
color  and  a  white  streak  Its  hardness  is  5  or  6  and  its  specific  gravity 
about  3  i  Translucent  crystals  are  strongly  pleochroic  in  deep  blue 
and  greenish  blue  tints — the  former  when  viewed  along  the  vertical 


axis  Their  indices  of  refraction  for  yellow  light  are  a=  i  603,  /?=  i  632, 
7=i  639 

In  the  closed  tube  lazuhte  swells,  whitens  and  yields  water  When 
heated  in  the  blowpipe  flame  it  whitens,  falls  to  pieces  and  colors  the 
flame  bluish  green  The  white  powder  moistened  with  Co(NOs)2  and 
reheated  regains  its  blue  color.  When  moistened  with  HgSC^  and 
heated  in  the  blowpipe  flame  it  imparts  to  it  a  green  blue  color  It  is 
infusible  and  is  unacted  upon  by  acids 

Lazulite,  when  massive,  closely  resembles  in  appearance  massive 
forms  of  some  varieties  of  sodahte,  hauymte  and  lazunte  (p  333)  The 
latter,  however,  are  soluble  in  HC1.  Moreover,  none  of  them  contains 

Occurrence  —  The  mineral  occurs  in  quartz  veins  in  sandstones  and 
slates  and  is  usually  a  product  of  metamorphism  It  is  sometimes,  how- 
ever, found  in  serpentine  rocks,  with  corundum,  in  which  case  it  may  be 

Localities  —  Good  crystals  occur  at  Kneglach,  in  Styna,  at  Horrs- 
joberg,  in  Sweden,  and  in  the  United  States  at  Crowder's  Mountain, 
North  Carolina,  and  on  Graves  Mountain  m  Georgia, 


The  ohvenite  group  includes  a  number  of  basic  copper,  lead  and 
zinc  compounds  of  the  general  formula  R"o(OH)R'"04  m  which  R" 
=  Cu,  Zn,  Pb  and  R'"=As,  P,  V      The  group  is 
orthorhombic  (bipyramidal  class),  with  axial  ratios 
approximating   95  .  i     70     The  most   important 
members  of  the  group  are  the  two  copper  min- 
erals, ohvemte,   Cu(CuOH)  As04  and  libethemte, 

Ohvenite  occurs  m  fibrous,  globular,  lamellar, 
granular  and  earthy  masses  and  in  prismatic  and 
acicular  crystals  bounded  by  oo  P(uo),  oo  P  60  (100), 
oo  P  06  (oio),  P  &  (on)  and  P  56  (101)  (Fig  158) 
Their  axial  ratio  is  9396  i  .  6726  and  the  angle 
1 10  A 1 10=  86°  26'.  Their  cleavage  is  poor. 

The  mineral  is  some  shade  of  green,  brown, 
yellow  or  grayish  white  and  its  streak  is  olive-green 
m  greenish  varieties.    It  is  transparent  to  opaque,  is  brittle,  has  a 
hardness=3,  and  a  specific  gravity =4.3.    Its  refractive  indices  for 

to  158  — Ohvenite 
Crystal  with  oo  Poo, 
zoo  (a),  oo  p,  no 
(m),  oo  Poo  ,010  (6), 
P  oo ,  on  (e)  and 
P  55 ,  101  (») 


ydlow  light  are  about  i  83.  Its  luster  is  usually  vitreous  Fibrous 
vaneties  are  sometimes  known  as  wood-copper 

Ohvemte  fuses  easily  (2)  to  a  mass  that  appears  crystalline  on  cooling 
It  gives  the  usual  reactions  for  EkO,  Cu,  and  As  It  is  soluble  in  acids 
and  in  ammonia 

It  is  associated  with  other  copper  compounds  in  some  copper  ores 
Its  ongin  is  secondary  in  all  cases  It  occurs  in  the  Tmtic  district, 
Utah,  and  in  many  copper  veins  in  Europe  and  in  South  America 

Libethenite  occurs  in  compact  or  globular  masses  and  in  small 
crystals  that  resemble  those  of  ohvemte     Their  axial  ratio  is  9605  : 
i     7019  and  no  A  110=87°  40' 

The  mineral  is  bnttle  Its  fracture  is  indistinctly  conchoidal  Its 
color  is  dark  ohve-green  and  its  streak  a  lighter  shade  It  is  translucent 
or  transparent  and  has  a  resinous  luster  Its  hardness =4  and  sp  gr 
=37.  Its  intermediate  refractive  index  for  yellow  light  is  i  743 

When  heated  in  the  closed  tube  it  yields  water  and  blackens  It  is 
easily  fusible  (2)  It  yields  the  usual  reaction  for  Cu  and  P,  and  is  sol- 
uble m  acids  and  in  ammonia  It  is  distinguished  from  ohvemte  by  the 
reaction  for  phosphorus 

It  occurs  at  many  of  the  localities  for  ohvemte,  where,  like  this  min- 
eral, it  is  a  decomposition  product  of  other  copper  compounds. 

Eerderite  (CaBe(OH'F)P04) 

Herdente  is  an  isomorphous  mixture  of  the  two  phosphates,  CaBeFP04 
and  CaBe(OH)P04.  The  latter  molecule  occurs  in  nature  as  hydro- 
kerdente,  the  former  occurs  only  in  mixtures  The  theoretical  compo- 
sition of  the  fluorine  (I)  and  bydroxyl  (II)  molecules  and  of  transparent 
crystals  from  Stoneham  (III),  and  Pans  (IV),  Maine,  are  given  below 

BeO        CuO        P205          F          H20        Ins. 

.       .  .  100 

5  59          -  ioo 

3  70  99  67 

44          ioo  51 

The  mineral  is  found  only  in  crystals,  which  are  monoclmic,  with 
a :  b  :  $=.6301 :  i :  .4274  and  £=89°  $4*.  Their  habit  is  hexagonal, 
pyramidal  or  short  prismatic,  elongated  in  the  direction  of  a 

I-  IS  39 

34  33 

43  53 

ii  64 

II.  15  53 

34  78 

44  10 

III.  15  51 

33  67 

43  74 

5  27 

rv.  16  13 

34  04 

44  OS 



Herdente  is  colorless  or  light  yellow,  transparent  or  translucent 
Its  refractive  indices  are  a=  i  592,  /3=  i  612,  y=  i  621 

Its  density  is  about  3,  diminishing,  as  the  amount  of  hydroxyl  in- 
creases, to  2  952  in  the  pure  hydroherderite 

Before  the  blowpipe  herderite  first  phosphoresces  with  an  orange- 
yellow  light,  then  fuses  to  a  white  enamel,  colors  the  flame  red  and  yields 
fluorine  In  the  closed  glass  tube  most  specimens  yield  an  acid  water, 
which,  when  strongly  heated,  evolves  fluorine  that  etches  the  glass 
The  mineral  also  reacts  for  phosphorus  with  magnesium  nbbon  It  is 
slowly  soluble  in  HC1 

Occurrence^  Origin  and  Uses  — Herderite  occurs  m  pegmatite  dikes 
at  Stoneham,  Hebron,  and  other  places  in  Maine,  and  at  the  tin  mines  of 
Ehrenfriedersdorf,  Saxony,  in  all  of  these  places  it  is  apparently  of 
pneumatolytic  origin  The  material  from  Maine  is  used  to  a  small 
extent  as  a  gem  stone 


Acid  phosphates  are  those  m  which  all  of  the  hydrogen  atoms  of  the 
acids  have  not  been  replaced  by  metals  or  by  basic  radicals  Theoret- 
ically, they  contain  replaceable  hydrogen  atoms  There  are  12  or  15 
minerals  that  are  thought  to  belong  to  this  class,  but  the  composition 
of  many  of  them  is  very  obscure  Most  of  them  appear  to  be  hydrated 
The  only  important  mineral  that  may  belong  to  the  class  is  the  popular 
gem  stone,  turquoise.  This,  according  to  the  best  analyses,  contains  its 
components  in  the  proportions  indicated  by  the  formula  CuO,  3Al2Os, 
2P2Os,  9H20,  which  may  be  interpreted  as  (CuOH)(Al(OH)2)6H5(P04)4, 
which  is  4(HsP(>4),  in  which  6  hydrogen  atoms  are  replaced  by  6Al(OH)s 
groups  and  one  by  the  group  CuOH. 

Turquoise  ((CuOH)(Al(OH)2)6H5(P04)4) 

Turquoise  is  apparently  a  definite  compound  of  the  formula  indicated 
above,  which  requires  34 12  per  cent  P20s,  36  84  per  cent  Al20a,  9  57 
per  cent  CuO  and  19  47  per  cent  H20  Analysis  of  a  crystallized  variety 
from  Lynch,  Campbell  Co  ,  Virginia,  gave 

P205  A1203        Fe203         CuO  H20       Total 

34  13  36  5°  2I  9  °°  20  I2      99  96 

Most  specimens,  however,  have  not  as  simple  a  composition  as  this 
They  are  probably  isomorphous  mixtures  of  unidentified  phosphates. 


The  mineral  as  usually  found  is  apparently  an  amorphous  or  cryp- 
tocrystalline,  translucent  or  opaque  material  with  a  wa\y  lustei  and  a 
sky-blue,  green  or  greenish  gray  color  Material  recently  found  at 
Lynch,  Virginia,  however,  occurs  in  minute  tnclmic  crystals  with  an 
axial  ratio  7910  .  i  6051,  \Mtha=87°o2/?/3=86°  2q',  and  7=  72°  19' 
Their  habit  is  pyramidal  with  ooP  60(100),  oop  06(010),  oo  'P(iTo), 
ooP'(no)  and  POO  (oil) 

The  fracture  of  turquoise  is  conchoidal.  It  has  a  hardness  of  5-6 
and  a  specific  gravity  between  261  and  2  89  It  is  brittle,  and  has  cleav- 
ages in  two  directions.  The  determined  refractive  indices  of  the  Vir- 
ginia crystals  are:  a=i.6i,  7=  1.65 

In  the  closed  tube  the  mineral  decrepitates,  yields  water  and  turns 
black  or  brown  It  is  infusible,  but  it  assumes  a  glassy  appearance  when 
heated  before  the  blowpipe  and  colors  the  flame  green.  When  moistened 
with  HC1  and  again  heated  the  flame  is  tinged  with  the  azure  blue  of 
copper  chloride  The  mineral  reacts  for  copper  and  phosphoric  acid 
Some  specimens  dissolve  m  HC1,  but  the  crystallized  material  from  Vir- 
ginia is  insoluble  until  after  it  is  strongly  ignited  It  partly  dissolves 
in  KOH,  with  the  production  of  a  brown  residue  of  a  copper  compound 

Occurrence  — Turquoise  occurs  in  thin  veins  cutting  through  certain 
decomposed  volcanic  rocks  and  other  rocks  in  contact  with  them, 
and  in  grains  disseminated  through  them,  in  stalactites,  globular 
masses  and  crusts  It  is  probably  an  alteration  product  of  other  com- 

Localities  — Turquoise  is  found  in  narrow  veins  and  irregular  masses 
in  the  brecciated  portions  of  acid  volcanic  rocks  and  the  surrounding  clay 
slates,  near  Nish&pur,  in  Persia,  in  the  Megara  Valley,  Sinai,  and  near 
Samarkand,  in  Turkestan  In  all  these  places  the  mineral  is  of  gem 
quality  and  until  recently  nearly  all  the  gem  turquoise  came  from  them 
Within  late  years  gem  turquoise  has  been  discovered  in  the  Cenllo  Moun- 
tains, near  Santa  Fe,  New  Mexico,  where  it  has  been  mined  in  consid- 
erable quantity  The  locality  is  the  site  of  an  ancient  mine  which  was 
worked  by  the  Mexicans  It  is  also  found  and  mined  in  the  Burro 
Mountains,  Grant  County,  in  the  same  State,  near  Millers,  and  at  other 
points  in  Nevada  and  near  Mineral  Park,  Mohave  County,  Arizona, 
where  also  the  ancient  Mexicans  once  had  mines  At  La  Jara,  Conejos 
County,  Colorado,  old  mines  have  likewise  been  opened  up  and  are  now 
yielding  gem  material 

Uses  —The  only  use  of  turquoise  is  as  a  gem  stone  Though  much 
of  the  American  mineral  is  pale  or  green,  some  of  it  is  of  as  fine  color  as 
the  Oriental  stone  A  favorite  method  of  using  the  stone  is  in  its 


matrix      Small  pieces  of  the  rock  with  its  included  turquoise  are  pol- 
ished and  sold  under  the  name  of  turquoise  matrix 

Production  —  The  total  value  of  the  turquoise  and  turquoise  matrix 
produced  in  the  United  States  during  1911  was  $44,751  This  weighed 
about  4,363  pounds  In  several  previous  years  the  production  reached 
about  $150,000,  but  in  1912  it  was  valued  at  only  $10,140 


Of  the  hydrous  salts  of  orthophosphonc  and  orthoarsemc  acids  there 
are  two  which  are  of  some  importance  because  they  are  fairly  common, 
a  third  which  is  utilized  in  jewelry,  and  a  fourth  that  is  important  as  an 
indicator  of  the  presence  of  an  ore  of  cobalt.  The  first  two  are  wwanite 
and  scorodtte,  a  phosphate  and  an  arsenate  of  iron,  the  third  is  vanszite, 
an  aluminium  phosphate,  and  the  fourth  is  erytknte,  an  arsenate  of 
cobalt  A  dimorph  of  vanscite,  known  as  lucmite,  is  rare  All  give 
water  in  the  closed  tube  and  yield  phosphine  when  fused  with  magne- 
sium and  moistened  with  water 


The  only  important  group  of  the  hydrated  orthophosphates  and 
orthoarsenates  is  that  of  which  viviamte  and  erythnte  are  members. 
The  general  formula  of  the  group  is  R"3(R'"04)2  8H20  in  which  R" 
=Fe,  Co  Ni,  Zn  and  Mg,  and  R'"=P  or  As  Although  some  members 
have  not  been  found  in  measurable  crystals,  crystals  of  all  have  been 
made  in  the  laboratory,  so  that  there  is  little  doubt  of  their  isomorphism. 
All  are  monochmc  prismatic  with  axial  ratios  of  about  75  •  i  :  70  and 
ft  about  74°  The  group  is  as  follows 

Bob^ente,  Mg3(P04)2  8H20  ErytMte,  Co3(As04)2  8H20 

Hornes^te,  Mg3(As04)2  8H20  Annabcrgde,  Nm(As04)2  8H20 

Vtwamte,  Fe3(P04)2  8H20  Cabrente,  (Ni  Mg)3(As04)2  8H2O 

Symplestte,  Fe3(As04)2  8H20  Kottigite,  Zn3(As04)2  8H20 

Only  vivianite,  erythnte  and  annabergite  are  described 

Vivianite  (Fe3(P04)2  8H2O) 

Vivianite  is  a  common  phosphate  of  iron  It  occurs  not  only  in  dis- 
tinct crystals  but  also  as  bluish  green  stains  on  other  minerals,  and  as 
an  invisible  constituent  of  certain  iron  ores,  thereby  diminishing  their 


Its  formula  indicates  the  presence  of  43  per  cent  FeO,  28  3  per  cent 
P20s  and  28  7  per  cent  BkO 

Viviamte  crystals  are  monoclmic  (prismatic  class),  usually  with  a 
prismatic  habit  Their  axial  ratio  is  7498  .  i  7015,  and  £=75°  34' 
The  principal  forms  observed  on  them  are  oo  P  56  (100),  oo  P  ob  (oio), 
ooP(no),  °oP3(3io),  P&O(IOI),  P(III)  and  oP(ooi)  The  angle 
uoAi"io=7i°  58'  The  mineral  also  occurs  in  stellate  groups,  in  glob- 
ular, fibrous  and  earthy  masses  and  as  crusts  coating  other  compounds 

Its  cleavage  is  perfect  parallel  to  oo  P  «D  (oio)  It  is  flexible  in 
thin  splinters  and  sectile.  The  fresh,  pure  mineral  is  colorless  and  trans- 
parent, but  specimens  usually  seen  are  more  or  less  oxidized  and  have 
a  blue  or  green  color  It  has  a  vitreous  to  pearly  luster  Its  streak  is 
white  or  bluish,  changing  to  indigo-blue  or  brown  on  exposure  to  the  air 
Its  pleochroism  is  strong  in  blue  and  pale  yellow  tints  Its  hardness 
is  i  5-2  and  density  about  2  6.  Its  refractive  indices  for  yellow  light 
are  a=i  5818,  jS-i  6012,  7-1  6360 

In  the  closed  tube  viviamte  whitens,  exfoliates  and  yields  water  at  a 
low  temperature  It  fuses  easily  (2),  tingemg  the  flame  bluish  green 
Its  fusion  temperature  is  1114°.  The  fused  mass  forms  a  grayish  black 
magnetic  globule.  It  gives  the  reaction  for  iron,  and  is  soluble  in  HC1 

The  mineral  is  easily  recognized  by  its  softness,  easy  fusibility  and 
by  yielding  the  test  for  phosphorus. 

Synthesis  — Crystals  have  been  made  by  heating  iron  phosphate  with 
a  great  excess  of  sodium  phosphate  for  eight  days 

Occurrence  and  Origin. — Vivianite  occurs  in  veins  of  copper,  tin  and 
gold  ores;  disseminated  through  peat,  clay,  and  limomtc,  coating  the 
walls  of  clefts  in  feldspars  and  other  minerals  of  certain  igneous  rocks, 
and  partially  filling  cavities  in  fossils  and  partly  fossilized  bones  It  is 
usually  the  result  of  the  decomposition  of  other  minerals 

Localities, — Crystals  are  found  at  several  points  m  Cornwall,  Eng- 
land, at  the  gold  mines  at  Verespatak,  in  Transylvania,  at  Allentown, 
Monmouth  County,  New  Jersey,  and  at  many  other  places  The  earthy 
variety  occurs  at  Allentown,  Mullica  Hill  and  other  points  in  New  Jer- 
sey, in  Stafford  County,  Virginia,  and  in  swamp  deposits  at  many  places 
It  is  abundant  in  limomte  at  Vaudreuil,  in  Quebec,  and  in  bog  iron  ores 

Erythrite  (Co3(As04)2  8H20) 

Erythnte,  or  cobalt  bloom,  isinot  a  common  mineral,  but,  because 
of  its  beauty  and  the  fact  that  it  is  the  usual  alteration  product  of  cobalt 
ores,  it  deserves  to  be  described 


In  composition  erythnte  is  37  5  per  cent  CoO,  38  4  per  cent  As205, 
and  24  i  per  cent  H20  It  usually,  ho\\e\er,  contains  some  iron,  nickel 
and  calcium 

The  mineral  is  isomorphous  with  vivianite  Its  crystals  are  mono- 
climc  and  prismatic  or  acicular  and  their  axial  ratio  is  7037  i  •  7356 
and  jS=74°  51'  The  pnsms  are  stnated  vertically  Erythrite  occurs 
in  all  the  forms  in  which  vivianite  is  found  Its  crystals  are  usually 
bounded  by  ooP  03(010),  ooP(no),  oop  66(100),  +Po6(Toi)  and 

The  cleavage  of  erythnte  is  perfect  parallel  to  oo  P  ob  (oio)  It  is 
transparent  or  translucent,  has  a  gray,  crimson  or  peach-red  color, 
and  a  white  or  pink  streak  Its  hardness  varies  between  i  5  and  2  5 
and  its  density  is  295  Its  luster  is  pearly  on  oo  Poo  (oio)  and 
vitreous  on  other  faces  It  is  flexible  and  sectile.  Its  refractive 
indices  for  yellow  light  are  a—  i  6263,  0=  i  6614,  7=  i  6986 

In  the  closed  tube  ery  thrite  turns  blue  and  yields  water  at  a  low  tem- 
perature At  a  high  temperature  it  yields  As20<j,  which  condenses  in 
the  cold  portion  of  the  tube  as  a  dark  sublimate  It  fises  at  2,  and 
tinges  the  flame  pale  blue  On  charcoal  it  fuses,  yields  arsenic  fumes  and 
a  gray  globule  which  colors  the  borax  bead  a  deep  blue  The  mineral 
is  soluble  in  HC1,  giving  rise  to  a  pink  solution,  which,  upon  evaporation 
to  drynesSj  gives  a  blue  stain 

It  is  easily  recognized  by  its  color  and  the  cobalt  reaction.  It  is 
readily  distinguished  from  pink  tounna\ne  (p  434),  by  its  hardness 
and  easy  fusibility 

Synthesis  —  Crystals  have  been  obtained  by  carefully  mixing  to- 
gether warm  solutions  of  CoSO-i  and  HNa2As04  7HsO 

Occurrence  —  Erythnte  occurs  in  the  upper  portions  of  veins  con- 
taining cobalt  minerals,  being  formed  by  their  weathering 

Localities  —  Tt  occurs  as  scales  and  crystals  at  Schneeberg,  Saxony, 
and  as  crystals  at  Modum,  Norway.  It  is  found,  also,  at  Lovelock's 
Station,  Nevada,  at  several  points  m  California  and  in  large  quantities 
at  Cobalt,  Ontario. 

Annabergite  (Ni3(As04)2-8H20) 

Annabergite,  or  nickel  bloom,  is  isomorphous  with  erythnte  It 
occurs  massive,  disseminated  m  tiny  grains  through  certain  rocks,  as 
crusts  and  stains  m  globular  and  earthy  masses,  and  in  fibrous  crystals, 
the  axial  ratios  of  which  are  not  known. 

The  mineral  is  apple-green  in  color,  and  is  translucent  or  opaque. 


Its  streak  is  light  green  Its  luster  is  vitreous,  its  hardness,  i  5-2  5 
and  sp  gr  =3 

Before  the  blowpipe  it  melts  to  a  gray  globule  and  gives  the  arsenic 
odor  In  the  closed  glass  tube  it  blackens  and  yields  water  In  the 
beads  it  gives  the  usual  reactions  for  Ni  The  mineral  dissolves  easily 
in  acids 

Synthesis  —Crystals  have  been  produced  by  the  method  employed 
in  the  synthesis  of  erythnte,  using  NiSO-i,  instead  of  CoSC>4 

Occurrence  — It  is  found  as  a  common  alteration  product  of  nickel- 
bearing  minerals,  in  the  oxidized  portions  of  veins 

Localities  — Its  best  known  occurrences  are  m  Allemont,  Dauphme, 
Annaberg  and  Schneeberg,  Saxony,  Cobalt,  Ontario,  and  mines  in 
Colorado  and  Nevada. 

Variscite  (A1P04  2H20) 

Vanscite  is  a  bright  green  mineral  that  has  recently  come  into  use  as 
a  gem  material.  It  is  apparently  an  aluminium  phosphate  with  a 
theoretical  composition  as  follows  449  per  cent  P20r>,  32  3  per  cent 
AloOa  and  228  per  cent  H^O  A  specimen  of  crystallized  material  from 
Lucm,  Utah,  gave  the  following  analysis 

P205          A1203         Fe203        Cr03  V203        H20          Total 

44  73          32  40  06  18  32        22  68         100  37 

Recent  investigations  indicate  that  the  compound  A1P04  2H20  is 
dimorphous  Both  forms  are  orthorhombic  but  one,  vanscite,  has  the 
properties  described  under  this  heading  The  other,  lucinite,  is  associ- 
ated with  vanscite,  near  Lucm,  Utah.  It,  however,  occurs  in  crystals 
that  are  octahedral  in  habit,  rather  than  tabular,  and  that  have  an 
axial  ratio  of  8729  i  9788  In  other  respects  lucimte  is  very  much 
like  variscite 

An  amorphous  variety  of  the  same  substance  is  also  known  It 
occurs  as  a  white,  pale  brown  or  pale  blue  earthy  mass  with  a  sp  gr  of 
2.135  It  differs  from  the  crystalline  varieties  in  being  completely 
soluble  in  warm  concentrated  H2S04 

The  crystals  of  vanscite  are  orthorhombic  and  are  bounded  by 
co  P  66  (oio),  oo  P(no)  and  £P  oo  (012),  and  in  a  few  cases  oo  P  60  (too) 
Their  axial  ratio  is  8944  .1:1 0919  Nearly  all  crystals  are  tabular 
parallel  to  oo  P  56  (oio)  Twins  are  common,  with  |P  60  (102)  the 
twinning  plane  Crystals  are  comparatively  rare,  the  mineral  occur- 
ring usually  in  fibrous  or  finely  granular  masses  and  as  incrustations 


Vanscite  vanes  in  color  from  a  pale  to  a  bright  green  It  is  weakly 
pleochroic,  has  a  vitreous  luster,  a  hardness  of  about  4  and  a  density  of 
2  54  Its  refractive  indices  for  yellow  light  are  a=i  546,  /3=i  556, 
r=i  578 

Before  the  blowpipe  the  mineral  is  infusible  It,  however,  whitens 
and  colors  the  flame  deep  bluish  green  It  )ields  water  in  the  closed 
tube,  and  with  the  loss  of  its  water,  it  changes  color  from  green  to 
lavender  The  same  change  in  color  takes  place  gradually  at  temper- 
atures between  iio°-i6o°  When  heated  with  Co(N03)2,  it  turns  blue 
and  when  fused  with  magnesium  ribbon  it  gives  the  test  for  phosphorus 
It  forms  a  yellowish  green  glass  with  borax  or  microcosmic  salt.  The 
mineral  is  insoluble  in  acids  before  heating 

Vanscite  resembles  m  some  respects  certain  varieties  of  turquoise 
and  wwuellite  (p  287)  It  is  distinguished  from  turquoise  by  the  absence 
of  copper  and  from  wavellite  by  its  insolubility  in  acids 

Occurrence  —  The  mineral  occurs  as  a  cement  in  a  brecciated,  cherty 
limestone  and  a  brecciated  rhyolite,  as  nodules  m  the  cherty  portions 
of  the  breccias  and  also  as  veins  traversing  these  rocks  It  is  also 
found  as  nests  in  weathered  pegmatites  The  crystals  occur  as  coarsely 
granular,  loosely  coherent  masses  in  more  compact  granular  masses 

Localities  —  Vanscite  occurs  at  Messbadi,  Sa\ony,  in  Montgomery 
County,  Arkansas,  near  Lucm,  Utah,  and  at  a  number  of  other  places 
in  Tooele  and  Washington  Counties  in  this  State,  in  Esmeralda  County, 
Nevada,  and  m  Montgomery  County,  Arkansas  The  colloidal  vanety 
occurs  as  concretions  in  slates  at  Brandberg,  near  Leoben,  Austria 

Uses  —  The  mixture  of  vanscite  and  rock  is  cut,  and  employed  as 
sets  in  necklaces,  belt  pins,  etc  ,  under  the  names  "  utahlite  "  and 
"  amatrice,"  but  because  of  the  softness  of  the  vanscite  it  cannot  be 
used  with  success  for  all  the  purposes  for  which  turquoise  matrix  is 

Production  —  The  production  of  the  material  in  the  United  States 
during  1911  was  540  Ib  ,  valued  at  $5,750  In  the  previous  year 
5,377  Ib  were  reported  as  having  been  sold  for  $26,125,  In  I9I2> 
the  amount  marketed  was  valued  at  $8,150. 


Skorodite  is  more  common  than  viviamte  It  occurs  in  globular 
and  earthy  masses,  as  incrustations,  and  in  crystals  of  a  green  or  brown 
color  The  globular  forms  are  colloidal 

Its  formula  indicates  Fe203=346  per  cent,  Asa03=498  Per  cent 


and  HoO=  15  6  per  cent     An  incrustation  on  the  deposits  of  the  Joseph's 
Coat  Spring,  Yellowstone  National  Park,  consisted  of 

As2O5  Fe2O3  H2O  SiO2  SO3         Total 

46  48  33  29  I5  5°  4  35  84        100  46 

Its  crystallization  is  orthorhombic  (bipyramidal  class),  with  a  b  .  c 
—  8658  .  i  9541.  The  crystals,  which  are  commonly  bounded  by 
oo  P  60(100),  oo  P  06(010),  ooPa(i2o),  ooP(uo), 
P(III)  and  -2-P(ii2),  are  either  prismatic  or  octa- 
hedral m  habit  (Fig  159)  The  angle  niAiTi 
=  65°  20'  Their  cleavage  is  imperfect,  parallel  to 

The  mineral  is  brittle     It  has  a  vitreous  luster, 
a  leek-green  or  liver-brown   color    and   a  white 
streak.    It  is  translucent  and  has  an  uneven  frac- 
ture    Its  hardness  is  3  5-4  and  density  about  3  3 
FIG    159  —Skorodite  The  colloidal  phases  are  somewhat  softer  than  the 
Crysta  wit   oo     co ,  crysta}}me  phases 
100  (a)     oo  P 2,  1 20 

(d)  and  P  m  (p)         In  "the  closed  tube  skorodite  turns  yellow  and 

'  yields  water     It  fuses  easily,  coloring  the  flame 

bluish.    On  charcoal  it  yields  white  arsenical  fumes  and  gives  a  black 

porous,  magnetic  button    It  is  soluble  in  HC1,  forming  a  brown  solution 

It  is  distinguished  from  wviamte  by  the  arsenic  test,  and  from  dufren- 

%te  by  its  streak  and  reaction  in  the  closed  tube 

Synthesis  — Skorodite  crystals  have  been  made  by  heating  metallic 
iron  with  concentrated  arsenic  acid  solution  at  I4o0~i$o0 

Occurrence. — Skorodite  is  frequently  associated  with  arsenopynte, 
in  the  oxidized  portions  of  veins  containing  iron  minerals  It  is  found 
also  in  a  few  places  as  incrustations  deposited  by  hot  springs, 

Localities — It  occurs  m  fine  crystals  at  Nerchinsk,  Siberia;  at 
Loelling,  m  Cannthia,  near  Edenville,  New  York,  in  the  Tmtic  dis- 
trict, Utah,  and  as  an  incrustation  on  the  siliceous  sinter  of  the  geysers 
in  Yellowstone  Park. 


The  hydrated  basic  phosphates  and  arsenates  are  rather  more  nu- 
merous than  the  hydrated  normal  compounds,  but  most  of  them  are  rare 
One,  waveltite,  however,  is  a  handsome  mineral  that  is  fairly  common. 
Another,  pharmacosiderite,  an  iron  arsenate,  is  known  to  occur  at  a 
number  of  places  The  uramte  group  also  belongs  here  Its  members 


are  comparatively  rare,  but,  because  of  the  presence  of  uranium  in  them, 
they  are  of  considerable  interest 

Wavellite  ((A1(OH  F)3)(PO4)2  5H2O) 

Wavellite  rarely  occurs  in  crystals  It  is  usually  in  acicular  aggre- 
gates that  are  either  globular  or  radiating  (Fig  160)  The  few  crystals 
that  have  been  seen  are  orthorhombic  (bipyramidal  class),  with  an 
axial  ratio  of  5573  i  .  4057 

Its  composition  varies  widely,  and  frequently  a  fairly  large  portion 
of  the  OH  is  replaced  by  F,  and  a  portion  of  the  Al  by  Fe 

The  mineral  is  vitreous  in  luster  and  white,  green,  yellow,  brown  or 
black  in  color  Its  streak  is  white  It  is  brittle  and  translucent,  m- 

FIG  1 60  — Radiate  Wavellite  on  a  Rock  Surface 

fusible  and  insoluble  m  acids  Its  hardness  is  3  5  and  its  density  2.41. 
Its  intermediate  refractive  index  for  yellow  light  is  i  526. 

Heated  m  a  dosed  glass  tube,  wavelhte  yields  water,  the  last  traces 
of  which  react  acid  and  often  etch  the  glass  In  the  blowpipe  flame  the 
mineral  swells  up  and  breaks  into  tiny  infusible  fragments,  at  the  same 
time  tingeing  the  flame  green.  The  mineral  is  soluble  in  HC1  and 
H2SO4.  When  heated  with  HaS04  many  specimens  yield  hydrofluoric 
acid  When  heated  on  charcoal  and  moistened  with  Co(NOs)2  and 
reheated,  the  mineral  turns  blue. 

Wavellite  is  distinguished  from  turquoise,  which  it  sometimes 
resembles,  by  its  action  in  the  blowpipe  flame,  by  its  inferior  hardness 
and  its  manner  of  occurrence 

Occurrence  — Wavellite  occurs  as  radiating  bundles  on  the  walls  of 


cracks  in  various  rocks  and  as  globular  masses  filling  ore  veins  and  the 
spaces  between  the  fragments  of  breccias  It  is  probably  m  all  cases 
the  result  of  weathering 

Localities  —It  is  found  at  a  great  number  of  places,  especially  at 
Zbirow,  in  Bohemia,  at  Mmas  Geraes,  Brazil,  at  Magnet  Cove,  Arkan- 
sas, and  in  the  slate  quarries  in  York  County,  Penn. 

Pharmacosidente  ((FeOH)3(AsO4)2  5H2O) 

Pharmacosiderite  is  a  hydrated  ferric  arsenate,  the  composition  of 
which  is  not  firmly  established  It  usually  occurs  m  small  isometric 
crystals  (hextetrahedral  class),  that  are  commonly  combinations  of 

ooQoo(ioo)   and  — (in)     It  is  also  sometimes  found  in  granular 

masses     Its  cleavage  is  parallel  to  oo  0  °o  (100) 

The  mineral  is  green,  dark  brown  or  yellow.  Its  streak  is  a  pale 
shade  of  the  same  color  It  has  an  adamantine  luster  and  is  translucent. 
Its  hardness  =  25  and  sp  gr  =3  It  is  sectile  and  pyroelectnc  Its 
refractive  mde\,  «=i  676 

Pharmacosiderite  reacts  like  skorodite  before  the  blowpipe  and  with 

The  mineral  occurs  m  the  oxidized  portions  of  01  c  \  ems,  in  Cornwall, 
England,  at  Schneeberg,  Saxony,  near  SchemmU,  Hungai}  ,  and  in  the 
Tintic  district,  Utah. 


The  uramtes  are  a  group  of  phosphates,  arsenates  and  vanadates 
containing  uranium  m  the  form  of  the  radical  uranyl  (UOs)  which  is 
bivalent  The  members  of  the  group  are  either  tetragonal,  or  ortho- 
rhombic  with  a  tetragonal  habit  They  all  contain  eight  molecules  of 
water  of  crystallization  Only  three  members  of  the  group  are  of 
sufficient  interest  to  be  discussed  here  These  are  the  hydrated  cop- 
per and  calcium  uranyl  phosphates,  torbermte  and  aittumte  and  the 
potassium  uranyl  vanadate,  carnotite 

The  entire  group  so  far  as  its  members  have  been  identified  is  as 

Awlumte  Ca(U02)2(P04)2  8H20  Orthorhombic 

Uranospwite  Ca(U02}2(As04)2  SBfcO  Orthorhombic 

Torb&rmte  Cu(U02)2(P04)2  8H20  Tetragonal 

Zeunente  Cu(U02)2(As04)2  8H20  Tetragonal 

Uranocirate  Ba(U02)2(P04)2  8H20  Orthorhombic 

Camohte  (Ca 


The  uramtes  are  of  interest  because  of  their  content  of  uranium,  an 
element  which  is  genetically  related  to  radium 

Autunite  (CaCUCbMPO^  8H2O) 

Autunite  occurs  in  thin  tabular  crystals  with  a  distinctly  tetragonal 
habit,  and  in  foliated  and  micaceous  masses 

The  percentage  composition  corresponding  to  the  above  formula 
is  6  i  per  cent  CaO,  62.7  per  cent  UOs,  15  5  per  cent  PsOs  and  15  7  per 
cent  H2O 

Its  crystals  are  orthorhombic  (bipjrraimdal  class),  with  an  axial 
ratio,  p875  :  i  28517,  thus  possessing  interfacial  angles  that  closely 
approach  those  of  torbermte.  Its  crystals  are  bounded  by  oP(ooi), 
P  a  (101),  P  06  (on),  and  several  less  prominent  planes  Their  cleav- 
age is  very  perfect  and  the  cleavage  lamellae  are  brittle  The  luster  is 
pearly  on  the  base  and  vitreous  on  other  surfaces. 

The  mineral  is  lemon-yellow  or  sulphur-yellow  in  color,  and  its  streak 
is  yellow  It  is  transparent  to  translucent.  Its  hardness  is  2-2  5  and 
its  specific  gravity  about  3  2.  Its  refractive  indices  for  yellow  light  are. 

«  =  i  553,0=1  S7S>7=i577 

The  mineral  reacts  like  torbermte  before  the  blowpipe  and  with  acids, 
except  that  it  shows  none  of  the  tests  for  copper.  It  is  recognized  by  its 
color,  streak  and  specific  gravity 

Occurrence  —  Autunite  occurs  m  pegmatite  veins  and  on  the  walls 
of  cracks  in  rocks  near  igneous  intrusions,  especially  in  association  with 
other  uranium  compounds,  of  which  it  is  a  decomposition  product. 

Localities.  —  It  has  been  found  at  Johanngeorgenstadt,  Germany, 
at  Middletown  and  Branchville,  Conn  ,  in  the  mica  mines  of  Mitchell 
County,  North  Carolina,  and  coating  cracks  in  gneiss  at  Baltimore,  Md 

Torbernite  (CuCUOs^CPO^  -8H20) 

Torbermte  occurs  in  small  square  tables,  that  may  be  very  thin  or 
moderately  thick,  and  in  foliated  and  micaceous  masses. 

The  pure  mineral  contains  612  per  cent  UOs,  8  4  per  cent  Cu, 
15  i  per  cent  P20s  and  15.3  per  cent  H2<D,  but  frequently  a  part  of  the  P 
is  replaced  by  As 

Its  crystals  are  tetragonal  (ditetragonal  bipyramidal  class),  with 
a  c=  i  .  2  9361  They  are  extremely  simple,  their  predominating 
forms  being  oP(ooi)  and  POD  (101).  Less  prominent  are  ooPoo  (100), 
sPoo(2oi)  and  ooP(no)  Their  cleavage  is  perfect  parallel  to  oP 
The  cleavage  lamellae  may  be  almost  as  thin  as  those  of  the  micas 
but  they  are  brittle 


The  mineral  is  bright  green  in  emerald,  grass  or  apple  shades,  has  a 
lighter  green  streak,  is  translucent  or  transparent,  and  has  a  hardness 
of  2  25  and  a  specific  gravity  of  about  3  5  Its  luster  is  pearly  on  the 
basal  plane  but  nearly  vitreous  on  other  burfaces  It  is  strongly  pleo- 
chroic  in  green  and  blue. 

Torbermte  gives  reactions  for  Cu  and  P  and  yields  water  in  the 
closed  tube  The  bead  reactions  for  uranium  are  masked  by  those  of 
copper  The  mineral  is  soluble  in  HN03 

The  mineral  is  easily  recognized  by  its  color  and  other  physical 

Occurrence.  —  Torbermte  is  occasionally  found  as  a  coating  on  the 
walls  of  crevices  in  rocks  It  occurs  in  Cornwall,  England,  at  Schee- 
berg,  Saxony,  at  Joachimsthal,  Bohemia,  and  at  most  places  where  other 
uranium  minerals  exist  It  is  probably  in  all  cases  a  weathering  product. 

Carnotite  ((Ca  KsXTTC^MVO^  xHaO) 

Carnotite,  like  the  other  uramtes  described,  is  extremely  complex 
in  composition  It  may  be  an  impure  potassium  uranyl  vanadate,  or  a 
mixture  of  several  vanadates  in  which  the  potassium  uranyl  compound 
is  the  most  prominent  The  formula  given  above  indicates  its  com- 
position as  well  as  any  simple  formula  that  has  been  proposed  A 
specimen  from  La  Sal  Creek,  Colorado,  shows  the  mineral  to  be  essen- 
tially as  follows  ' 

UOs       CaO      BaO      K20      H20  at  105°  H20  above  105° 
18  05      54  oo      i  86      i  86      5  4^  3  16  2  21 

though  there  are  present  in  the  specimen  analyzed,  or  in  other  specimens 
from  the  same  locality,  also  As203,  P2O5,  Si02,  Ti02,  C02,  S03,  Mo03, 
Cr203,  Fe203,  A1203,  PbO,  CuO,  SrO,  MgO,  Li20  and  Na20,  and  there 
are  reported  in  them  also  small  quantities  of  radium  Radiographs 
taken  with  the  aid  of  carnotite  have  been  published,  which  are  almost 
as  clear  as  those  taken  with  pitchblende  The  complete  analysis  of  a 
specimen  from  the  Copper  Prince  Claim,  Montrose  Co  ,  Colo  ,  gave: 












10,  C02= 

U03        MoOg      Fe203 
52  25           23         i  77 

K20       H20-       H20+ 
6  73         2  59          3  06 

33,  S03=.i2,   CrOs=tr, 

i.  08 

8  34 



99  84 
20  and 


The  mineral  has  been  found  only  in  tiny  crystalline  grams,  so  that  its 
physical  properties  are  not  well  known  It  is  bright  yellow  in  color,  and 
is  completely  soluble  in  HNOs  If  to  the  nitric  acid  solution  hydro- 
gen peroxide  be  added  a  brown  color  will  appear  Or  if  the  solution 
is  filtered,  made  alkaline  by  ammonia  and  through  it  is  passed  H2S,  a 
garnet  color  will  develop  If  the  mineral  be  moistened  by  a  drop  of 
concentrated  HC1,  a  rich  brown  color  will  result  The  addition  of  a  drop 
or  two  of  water  will  change  the  color  to  light  green  or  make  it  disappear 

Occurrence — Carnotite  occurs  as  a  yellow  crystalline  powder,  some 
of  which  seems  to  consist  of  minute  crystals  with  an  hexagonal  habit, 
in  the  interstices  between  the  grains  in  sandstones  and  conglomer- 
ates, as  nodules  or  lumps  in  these  rocks,  and  as  coatings  on  the  walls 
of  cracks  in  pebbles  in  the  conglomerates  and  on  pieces  of  silicified 
wood  embedded  in  the  sandstones.  It  is  limited  to  very  shallow 
depths  and  is  apparently  a  deposit  from  ground  water. 

Localities — Its  principal  known  occurrences  are  in  Montrose,  San 
Miguel,  Mesa  and  Dolores  Counties  in  southwestern  Colorado,  especially 
in  Paradox  Valley,  and  in  adjoining  portions  of  New  Mexico  and  Utah, 
and  in  Rio  Blanco  and  Routt  Counties  in  the  northwestern  portion  of 
Colorado.  At  all  these  places  there  are  large  quantities  of  the  impreg- 
nated rock  but  it  contains  on  the  average  only  about  i  5  per  cent  to 
2  per  cent  of  UsOg.  The  mineral  has  also  been  described  from  Mt 
Pisgah,  Mauch  Chunk,  Pennsylvania,  and  from  Radium  Hill,  South 

Uses. — The  mineral  is  one  of  the  main  sources  of  radium  and  uranium 
and  is  one  of  the  principal  sources  of  vanadium.  Although  it  contains  a 
notable  quantity  of  uranium,  carnotite  has  little  value  except  as  an  ore 
of  radium  and  vanadium,  because  of  the  few  uses  to  which  uranium  is 
put.  This  metal  is  used  to  some  extent  in  making  steel  alloys  and  in  the 
manufacture  of  iridescent  glazes  and  glass  Its  compounds  are  used  in 
certain  chemical  determinations,  as  medicines,  in  photography,  as  por- 
celain paint,  and  as  a  dye  in  calico  printing.  The  uses  of  vanadium  have 
been  referred  to  on  p  273 

The  principal  value  of  carnotite  depends  upon  its  content  of  radium, 
which  in  the  form  of  the  chloride  is  valued  at  about  $40,000  per  gram 
or  $1,500,000  per  oz  The  importance  of  radium  as  a  therapeutic  agent 
has  not  been  established,  but  that  its  use  is  wonderfully  helpful  in  many 
diseases  is  beyond  question  Without  doubt  in  the  near  future  carno- 
tite will  become  the  principal  source  of  radium  in  the  world  Practically 
the  only  other  source  is  the  pitchblende  (p  297),  of  Gilpin,  Colorado, 
Cornwall,  England  and  Joachimsthal,  Austria. 


Production  —  Carnotite  has  been  mined  in  San  Miguel  and  Montrose 
Counties,  Colorado,  and  at  several  points  in  eastern  Utah,  but  mainly 
for  the  vanadium  it  contains  At  present  it  is  being  utilized  as  a  source 
of  radium  From  Colorado  8,400  tons  of  vanadium  ore,  with  a  value 
of  $302,000,  were  shipped  in  1911  and  from  New  Mexico  and  Utah  about 
70  tons,  valued  at  $3,500  Some  of  this,  however,  was  vanadmite 
Most  of  it  was  exported  and  used  as  a  source  of  vanadium  However, 
the  uranium  content  of  the  carnotite  mined  was  about  i  r  tons  of  the 
metal  During  1912  ore  containing  26  tons  of  uranium  o\ide  and  6  7 
grams  of  radium  was  produced  This  would  have  yielded  n  43  grams 
of  radium  bromide,  valued  at  $52,800  The  present  price  of  standard 
carnotite  carrying  at  least  2  per  cent  UgOg  and  5  per  cent  V^Os,  is  at  the 
rate  of  $i  25  per  Ib  for  the  former  and  thirty  cents  for  the  latter  In 
1914  the  selling  price  of  4,294  tons  of  carnotite  ore  containing  87  tons 
of  UsOg  was  $103  per  ton  At  the  present  time  nothing  is  paid  for  the 
radium  content  of  the  ore,  though  this  is  its  most  valuable  component 
One  ton  of  ore  containing  i  per  cent  of  UaOg  carries  2  566  milligrams  of 
radium  The  imports  of  uranium  compounds  during  191*2  were  valued 
at  $14,357- 


A  number  of  hydrated  acid  phosphates  and  arsenates  are  known  to 
constitute  an  isomorphous  group,  but  only  a  few  of  them  occur  as 
minerals.  Brushite  is  an  acid  calcium  phosphate  and  pfwrmacofate  is 
the  corresponding  arsenate  Both  crystallize  in  the  monoclimc  system 
(prismatic  class)  Neither  is  common 

Pharmacohte  (HCaAs04  2H20)  occurs  principally  in  silky  fibers,  in  * 
botryoidal  and  stalactic  masses  and  rarely  in  crystals  with  an  axial 
ratio  .6236  '  i :  3548  and  18=83°  13'.  Their  cleavage  is  perfect  par- 
allel to  oo  P  ob  (oio)  The  mineral  is  white  or  gray,  tinged  with  red 
Its  streak  is  white  It  is  translucent  or  opaque  Its  luster  is  vitreous, 
except  on  oo  P  &  (oio)  where  it  is  slightly  pearly  Thin  laminae  are 
flexible  Its  hardness  is  2-2  5  and  density  2  7  Its  refractive  indices 
for  yellow  light  are.  01=1.5825,  ]8=i  5891,  7=1  5937 

Before  the  blowpipe  pharmacohte  swells  up  and  melts  to  a  white 
enamel.  The  mineral  gives  the  usual  reactions  for  As,  EfeO  and  Ca  It 
usually  occurs  in  the  weathered  zone  of  arsenical  ores  of  Fe,  Ag  and  Co, 
at  Andreasberg,  Harz;  Joachimsthal,  Bohemia,  and  elsewhere. 


THE  rare  metah,  columbium  and  tantalum,  exist  in  a  few  silicates, 
but  their  principal  occurrences  are  as  columbates  and  tantalates  which 
are  salts  of  columbium  and  tantalum  acids,  analogous  to  the  various 
acids  of  sulphur  The  commonest  compounds  are  salts  of  the  meta- 
acids  EfeQteOo  and  H2Ta20e,  the  relations  of  which,  to  the  normal  acids, 
are  indicated  by  the  equation  2HsCb04— 2H20=H2Cb206  Other  im- 
portant minerals  are  derivatives  of  the  pyroacids  corresponding  to 
HiCtaOr,  or  2HsCb04— EkO  The  best  known  ortho  salt  is  ferguson- 
tte,  YCb04,  but  it  is  rare 

All  the  columbates  yield  a  blue  solution  when  partially  decomposed 
in  EfeSQi  and  boiled  with  HC1  and  metallic  tin  The  tantalates  when 
fused  with  KHSO*  and  treated  with  dilute  HC1  give  a  yellow  solution 
and  a  heavy  white  precipitate,  which,  on  treatment  with  metallic  zinc 
or  tin,  assumes  a  deep  blue  color  When  diluted  with  water  the  blue 
color  of  the  tantalate  solution  disappears,  whole  that  of  the  columbate 
solution  remains 

The  uranates  are  salts  of  uramc  acid,  HsUtX.  The  only  mineral 
known  that  may  be  a  uranate  is  urarnn/Ue9  and  the  composition  of  this 
is  doubtful. 

Columbite  (CFe-Mn)Nb2O6)  and  Tantalite  ((Fe-Mn)Ta2O6) 

These  two  minerals  are  isomorphous  mixtures  of  iron  and  manganese 
columbates  and  tantalates  The  name  columbite  is  applied  to  the  mix- 
ture that  is  composed  mainly  of  the  columbates,  and  tantalite  to  that 
which  is  principally  a  mixture  of  tantalates  When  the  tantalite  is 
composed  almost  exclusively  of  the  manganese  molecule,  it  is  known  as 
manganotantal^te  Tin  and  tungsten  are  frequently  found  in  both  min- 

Their  crystals  are  orthorhombic,  with  a  :  b  .  c—  8285  :  i  :  8898  for 
the  nearly  pure  columbium  compound,  and  8304 :  i  :  .8732  for  the 
nearly  pure  tantalum  compound  Both  form  short  prismatic  crystals 
containing  many  faces,  among  the  most  prominent  being  the  three 
pinacoids,  various  prisms,  notably  °o  P(no),  oo  Pjfoo)  and  oo  P6(i6o), 



and  the  domes  2?  56  (201)  and  |P  06  (012)  (Fig  161)  The  most  promi- 
nent pyramids  are  P(in)  and  P3(i33).  Twins  are  not  uncommon, 
with  2P66  (201)  the  twinning  plane  The  angle  noAiIo  for  colum- 
bite=79°  17' 

Both  minerals  are  usually  opaque,  black  and  lustrous,  and  occasion- 
ally iridescent,  though,  in  some  instances,  they  are  translucent  and 
broun  Their  streak  is  dark  red  or  black  Their  cleavage  is  distinct 
parallel  to  oo  P  60  (100),  fracture  uneven  or  conchoidal,  their  hardness 

6  and  their  specific  gravity 
between  5  3  and  73,  in- 
creasing with  the  propor- 
tion of  the  tantalum  mole- 
cules present  They  are 
both  infusible  before  the 
blowpipe  Some  specimens 
exhibit  weak  radioactivity 
When  columbite  is  de- 
composed by  fusion  with 
KOH  and  dissolved  in  HC1 

and   BkSO-i,   the    solution 
turns  blue  Qn  thfi  addltlon 

USbdllC  «1C      The  mm- 

eral  1S  also  partially  decom- 
posed when  evaporated  to 
dryness  with  EfeSCU,  forming  a  white  compound  that  changes  to  yellow 
When  this  residue  is  boiled  with  HC1  and  metallic  zinc  a  blue  solution 
results  The  mineral  also  gives  reactions  for  iron  and  manganese. 

Tantalite  is  decomposed  upon  fusion  with  KHSQ*  in  a  platinum 
spoon,  or  on  foil.  This  when  heated  with  dilute  HCl  yields  a  yellow 
solution  and  a  heavy  white  powder  Upon  addition  of  metallic  zinc,  a 
blue  color  results  and  this  disappears  on  dilution  with  water  In  the 
microcosmic  salt  bead  tantalite  dissolves  slowly,  giving  reactions  for  iron 
and  manganese  When  treated  with  tin  on  charcoal  the  bead  turns 

The  two  minerals  may  easily  be  confused  with  black  fourmahne 
(p.  434),  tlmemte  (p  462)  and  wolframite  From  tourmaline,  they  are 
distinguished  by  crystallization,  high  specific  gravity  and  luster,  from 
wolframite  by  their  less  perfect  deavage  and  by  the  reaction  with 
aqua  regia  (see  p  259),  from  ilmenite  by  the  test  for  titanium 

Occurrence,  Ongm  and  Localities.—  Both  minerals  occur  in  veins  of 
coarse  granite  and  probably  have  a  pneumatolytic  origin 

FIG    i6i.-Columbite  Crystals  with 

(a).    ooPoo,oio  (6),  oop,  no  (f»),   °oP2,  210 
Ml  -«     730  (d),  oop^o  (,),    |P  55,  I03 

(«,  P,  in  W  and  PI  133  M 


Columbite  is  found  in  granite  \erns  at  Bodenmais,  Bavaria,  Tam- 
mela,  in  Finland,  near  Limoges,  France,  with  tantahte,  near  Miask, 
in  the  Ilmen  Mountains,  Russia,  with  samarskite,  and  at  Ivigtut,  m 
Greenland  In  the  United  States  it  is  found  at  Standish  and  Stone- 
ham,  m  Maine,  at  Acworth,  in  New  Hampshire,  at  Haddam,  in  Con- 
necticut, at  Amelia  Court  House,  Virginia,  with  samarskite  in  the  mica 
mines  in  Mitchell  County,  North  Carolina,  m  the  Black  Hills,  South 
Dakota,  and  at  a  number  of  other  points  in  New  England  and  the  Far 

Tantahte  is  found  at  many  of  the  localities  for  columbite  and  also 
at  several  other  places  in  Finland,  near  Falun,  in  Sweden,  in  Yancy 
County,  North  Carolina,  and  m  Coosa  County,  Alabama 

Uses  — At  the  present  time  columbium  and  its  compounds  have  no 
commercial  uses  Tantalum,  however,  is  employed  in  the  manufacture 
of  filaments  for  certain  types  of  incandescent  lamps  Since,  howe\er, 
about  20,000  filaments  may  be  made  from  a  single  pound  of  the  metal  the 
market  for  tantalum  ores  is  very  limited 

Samarskite  and  Yttrotantalite 

These  two  minerals  may  be  regarded  as  isomorphous  mixtures  of 
salts  of  pyrocolumbic  and  pyrotantalic  acids,  in  which  the  bases  are 
yttrium,  iron,  calcium  and  uranyl. 

Samarskite,  according  to  this  view,  is  approximately 

Y2(Ca  Fe  U02)3(Nb207)3 

and  yttrotantalite  the  corresponding  tantalate  Yttrium  and  iron  are 
the  principal  bases,  but  there  are  also  often  present  erbium,  cerium, 
tungsten  and  tin 

Analyses  made  by  Rammelsberg  and  quoted  by  Dana  give  some  idea 
of  the  complexity  of  the  compounds: 


Ta206    Nb205     W03 

Sn02    Ti02*        Y203 


I  5  425 

46  25 

12  32       2  36 

I    12 


6  71 

II-  5  839 

14  36 

41  07 


56           6  10 

10  80 

III  5  672 


55  34 


i  08         8  80 








I     2    22 

i  61 


5  73 

6  31 

98  95 

II.  2  37 

10  90 

14  61 


too  93 

HI   4  33 

ii  94 

14  3° 


99  83 

I   Fromltterb; 

y,  Sweden 

II  From  North  Carolina 

HI  From  Miask 


*  Including  SiO*,  f  Including  Di20s  and  La^Os 


The  first  of  these  three  minerals  has  been  called  yttrotantahte  and 
the  other  two  samarslute  If  the  first  is  weathered,  as  seems  probable 
from  the  presence  of  over  SL\  per  cent  of  water,  the  three  may  constitute 
members  of  an  isomorphous  series  with  the  third  representing  the  nearly 
pure  columbate  (sanurskite),  the  first  a  compound  in  which  the  tantalate 
molecule  is  in  excess  (yttrotantahte),  and  the  second  an  intermediate 
compound  which  contains  both  the  tantalum  and  columbmm  molecules, 
with  the  latter  predominating 

With  more  accurate  analyses  the  great  complexity  of  these  compounds 
becomes  even  more  apparent  Hillebrand  has  given  the  following  report 
of  his  analysis  of  a  samarskite  from  Devil's  Head  Mountain,  near  Pike's 
Peak,  Colorado,  which  shows  the  futility  of  attempting  to  represent  its 
composition  by  a  chemical  formula- 

Pitch-black  Black  Weathered 

Variety  Variety  Variety 

Ta20fi  27  03  28  ii  19  34 

CbaOs  27  77  26  16  27  56 

W03  2  25  2  08  5  51 

SnO2  95  i  09                     82 

Zr02  2  29  2  60  3  10* 

U02  4  02  4  22 

U03  6  20 

Th02  3  64  3  60  3  19 

Ce203  54  49                      4i 

(La,Di)203  I  80  2  12  i  44 

Er20s  10  71  10  70  9  82 

Y203  6  41  5  96  5  64 

Fe203  8  77  8  72  8  90 

FeO  32  35                     39f 

MnO  78  75  \ 

ZnO  05  07  /   77 

PbO  72  80  i  07 

CaO  27  33  i  6 1 
MgO                                                                                „ 

K20  17  I3  •> 

(Na,Li)20  24  17  I  ^ 

H20..  i  58  i  30  3  94 

F  .  ?  ?                       ? 

99  75 

6    12 

f  O 


3P3>  231  W 


Both  samarskite  and  yttrotantahte  are  orthorhombic,  with  an  axial 
ratio  for  samarskite  of  5456  :  i  :  5178,  and  for  yttrotantahte,  5411  • 
i  .  i  1330.  They,  however,  more  commonly  occur  massive  and  in 
flattened  grams  embedded  in  rocks  Their  crystals  are  prismatic  in 
the  direction  of  the  c  or  the  b  a\is  Their  most  prominent  forms  are 
oo  P  56  (100),  oo  P  66  (oio)  and  P  65  (101)  (Fig  162)  Less  prominent 
but  fairly  common  are  *>P2(i2o),  ooP(no),  P(in)  and 
The  angle  noAiTo  for  samarskite  is  57°  14' 
and  for  yttrotantahte  56°  50' 

The  cleavage  of  both  minerals  is  indistinct 
parallel  to  oo  P  06  (oio)  Their  fracture  is 
conchoidal  Both  are  brittle  The  hardness  of 
samarskite  is  5-6,  its  density  about  5  7,  its 
luster  vitreous,  its  color  velvety  black  and  its 
streak  reddish  brown  Yttrotantahte  is  a  little 
softer  (5-5  5)  Its  specific  gravity  is  5  5~5  9, 
its  luster  submetallic  to  vitreous,  its  color  black,  FIG  162  —  SamarshteCiys- 
brown,  or  yellow,  and  its  streak  gray  to  color-  fed  w^  oop  55 , 100  (a), 
less  Samarskite  is  opaque  and  yttrotantahte  °°p55'  OI°  JW>  °°p» 
opaque  or  translucent 

The  reactions  of  the  minerals  vary  with 
their  composition  They  always  yield  the 
blue  solution  test  for  tantalum  or  columbium,  and  most  specimens  react 
for  Mn,  Fe,  Ti  and  U  The  reaction  for  uranium  is  an  emerald  green 
bead  with  microcosmic  salt  in  both  reducing  and  oxidizing  flame. 

They  are  distinguished  from  columbite  and  t&ntahte  by  the  form  of 
their  crystals. 

Occurrence — The  two  minerals,  like  columbite  and  tantahte,  are 
found  principally  in  pegmatite  veins  and  in  many  of  the  same  localities 
Yttrotantahte  occurs  mainly  at  Ytterby  and  near  Falun,  in  Sweden,  and 
samarskite,  near  Miask  in  the  Ilmen  Mountains,  Russia,  In  the  United 
States  the  last-named  mineral  is  sometimes  found  in  large  masses  in  the 
mica  pegmatites  of  Mitchell  County,  North  Carolina. 

Uses  — Neither  mineral  is  at  present  of  any  commercial  value.  They 
are,  however,  extremely  interesting  as  the  source  of  many  of  the  rare 
elements,  and,  especially,  as  a  possible  source  of  radium  and  closely 
related  substances. 


Uramnite,  or  pitchblende,  like  the  other  compounds  containing  the 
element  uranium,  is  of  doubtful  composition.  It  contains  so  many 


different  components  that  a  correct  conception  of  its  character  is  almost 
impossible  to  grasp  The  mineral  is  particularly  interesting  because  it 
always  contains  a  trace  of  radium,  of  which  it  is  an  important  com- 
mercial source  at  the  present  time 

Analyses   of   crystallized   material    (I)   from   Branchville,    Conn, 
and  from  Annerod  (II),  Norway  gave  the  following  results 

U03         U02      ThO2      PbO   Fe2O3    CaO   H2O       Pie       Insol 

I.  21  54      64  72      6  93      4  34        28        22        67      Und.  14 

II  30  63      46  13      6  oo      9  04        25        37        74  17         4  42 

\\ith  small  quantities  also  of  ZrC>2,  Ce02,  La203,  D^Os,  YgOs,  Er2C>3, 
MnO,  Alkalies,  SiOs  and  P20s  These  analyses  are  interpieted  as  indi- 
cating that  the  mineral  is  a  uranium  salt  of  uramc  acid,  U02(OH)2,  or 

H2U04,  thus   U^dr          ,  or  U30S,  in  which  Pb  replaces  the  U  in 

part,  and  Th02  the  UC>2  Radium  is  found  in  most  specimens  and 
helium  in  nearly  all 

Several  varieties  aie  recognized,  the  distinctions  being  based  largely 
upon  chemical  differences 

Broggente  has  UOa  to  other  bases  as  i  :  i 

Cleweite  and  nnvemte  contain  9  per  cent  to  10  per  cent  of  the  yttna 

Pitchblende  is  possibly  an  amorphous  urammte  containing  a  very 
little  thona  and  much  water  Its  specific  gravity  is  often  as  low  as  6  5, 
due  probably  to  partial  alteration 

Urammte  crystallizes  in  the  isometric  system  in  octahedrons,  and  m 
combinations  of  0(ui),  oo  0(no),  and  oo  0  oo  (100)  Crystals  are  rare, 
however,  the  material  usually  occurring  in  crystalline  masses  and  in 
botyroidal  groups 

The  mineral  is  gray,  brown  or  black  and  opaque.  Its  streak  is 
brownish  black,  gray  or  olive  green.  Its  luster  is  pitch-like  or  dull  Its 
fracture  is  uneven  or  conchoidal  It  is  brittle,  its  hardness  is  5  5  and 
density  9-9  7  Like  the  other  uranium  minerals  it  is  radioactive 

Before  the  blowpipe  uraninite  is  infusible.  Some  specimens  color 
the  flame  green  with  copper  With  borax  it  gives  a  yellow  bead  in  the 
oxidizing  flame,  turning  green  in  the  reducing  flame  All  specimens  give 
reactions  for  lead  and  many  for  sulphur  and  arsenic  The  mineral  is 
soluble  in  nitric  and  sulphuric  acids,  with  slight  evolutions  of  helium, 


the  ease  of  solubility  increasing  with  the  increase  in  the  proportion  of 
rare  earths  present 

Urammte  is  distinguished  from  wo'Jramite,  samarsktfe,  columbde  and 
tantahte,  by  lack  of  cleavage,  greater  specific  gravity,  and  differences  in 
crystallization  From  all  but  samarskite  it  is  also  distinguished  by  the 
reactions  for  uranium  and,  m  the  case  of  most  specimens,  by  the  reac- 
tion for  lead  It  is  especially  characterized  by  its  pitch-black  luster 

Occurrence  and  Localities  — Urammte  occurs  in  pegmatites  and  in 
veins  associated  ^ith  silver,  lead,  copper  and  other  ores  It  is  found  m 
the  ore  veins  in  Saxony,  Bohemia,  and  in  pegmatites  near  Moss,  Arendal 
and  other  points  in  Norway 

In  the  United  States  it  occurs  in  pegmatites  at  Middletown  and 
B ranch ville,  in  Connecticut,  at  the  Mitchell  County  mica  mines, 
North  Carolina,  and  at  Barnnger  Hill,  Llano  County,  Texas  It  is 
also  found  m  large  quantity  near  Central  City,  Gilpin  County,  Colorado, 
where  it  is  associated  with  gold,  galena,  tetrahednte,  chaicopynte  and 
other  ore  mineials 

Production  — Urammte  has  been  mined  in  small  quantity  in  Colo- 
rado, and  at  Barnnger  Hill,  both  as  a  source  of  uranium  and  as  a 
source  of  radium  In  Cornwall,  England,  and  at  Joachimsthal, 
Austria,  it  is  mined  as  a  source  of  radium  (See  also  p  292.) 



THE  silicates  are  salts  of  various  silicon  acids,  only  a  few  of  which 
are  known  uncombmed  with  bases  The  silicates  include  the  commonest 
minerals  and  those  that  occur  in  largest  quantity  They  make  up  the 
greater  portion  of  the  earth's  crust,  forming  most  of  the  igneous  rocks 
and  a  large  portion  of  vein  fillings  In  number,  the  silicates  exceed  all 
other  mineral  compounds,  but  because  of  their  stability  they  are  of  very 
little  economic  importance  A  few  are  used  as  the  sources  of  valuable 
substances,  and  their  aggregates,  the  sihcious  rocks,  are  utilized  as 
building  stones,  but,  on  the  whole,  they  are  of  little  commercial  value 
Since,  however,  they  occur  in  good  crystals  and  their  material  is  trans- 
parent in  thin  sections  so  that  it  can  easily  be  studied  by  optical  methods, 
they  are  of  great  scientific  importance  Much  of  the  progress  made  in 
crystallography  has  been  accomplished  through  the  study  of  these  com- 

Although  the  salts  of  the  silicic  acids  are  very  numerous  and  most  of 
them  are  very  stable  toward  the  ordinary  reagents  of  the  laboratory, 
the  acids  from  \\hich  they  are  derived  are  only  imperfectly  known 
The  only  one  that  has  been  prepared  m  the  pure  state  is  the  compound 
KfeSiOa  This  occurs  as  a  gelatinous  (colloidal)  white  substance  which 
rapidly  loses  water  upon  drying  and  probably  breaks  up  into  a  number 
of  other  compounds  which  are  also  acids,  containing,  however,  a  larger 
proportion  of  silicon  in  the  molecule  than  that  in  the  original  compound 
When  the  tetrafluoride,  or  the  tetrachionde,  of  silicon  is  decomposed  by 
water,  the  principal  product  is  the  acid  referred  to  above,  but  m  addition 
to  this  there  is  probably  formed  also  the  compound  HaSiO*  or  Si(OH)4, 
which  is  the  ortho  acid  Some  silicates  are  salts  of  these  acids.  Others 
are  salts  of  the  acids  containing  a  larger  proportion  of  silicon  In  most 
cases,  however,  these  acids  may  be  regarded  as  belonging  to  a  series  in 
which  the  members  are  related  to  one  another  m  the  same  manner  as 
are  normal  sulphuric,  common  sulphuric  and  pyrosulphuric  acids.  Nor- 
mal sxilphuric  acid  is  HeSOe  By  abstraction  of  aKkO  the  compound 
H2SO4,  or  ordinary  sulphuric  acid,  results  If  from  two  molecules  of 
EfcSOi,  one  molecule  of  HsO  is  abstracted,  1128307,  or  pyrosulphuric 
acid,  is  left.  In  the  same  manner  all  of  the  silicic  acids  may  be  regarded 



as  being  derived  from  normal  silicic  acid  Si(OH)4  or  H4SiO4  by  the  ab- 
straction of  water,  thus: 

Orthosilicic  acid  is 
Metasihcic  acid  is      H4Si04  -I^Oor  H2SiOs, 
Diorthosilicic  acid  is  2H4Si04—  IfeO  or 
Dimetasilicic  acid  is    21*28103-  EfeO  or 
Tnmetasilicic  acid  is  31128103  —  EfeO  or 

The  compounds  containing  more  than  one  silicon  atom  in  the  molecule 
are  known  as  polysilicates  The  salts  of  metasilicic  acid  are  meta- 

Many  attempts  have  been  made  to  discover  the  chemical  structure 
of  the  comparatively  simple  silicates  and  several  proposals  have  been 
offered  to  explain  the  great  differences  often  observed  in  the  properties 
of  silicates  with  the  same  empirical  formula,  but  no  explanation  of  these 
differences  has  thus  far  proved  satisfactory  The  silicates  are  so  very 
stable  under  laboratory  conditions,  and,  when  they  are  decomposed, 
their  decomposition  products  are  so  difficult  to  study,  that  it  has  been 
impossible  to  determine  their  molecular  volumes  or  to  understand  their 
substitution  products  We  are  thus  driven  to  ascribe  many  of  the 
anomalies  in  their  composition  to  solid  solutions,  to  absorption  phenom- 
ena, and  to  the  isomorphous  mixing  of  compounds,  some  of  which  do 
not  exist  independently 

There  are  many  silicates,  moreover,  which  cannot  be  assigned  to  any 
of  the  simple  acids  mentioned  above,  but  which  probably  must  be 
regarded  as  salts  of  very  much  more  complex  acids  Others  are  pos- 
sible salts  of  alurninosiliac  acids  in  which  aluminium  functions  in  the 
acid  portions  Thus,  albite  is  usually  regarded  as  a  trisilicate,  NaAlSisOg, 
and  anorthite  as  an  orthosihcate,  CaAl2(Si04)2  But  the  two  substances 
are  completely  isomorphous,  and  for  this  reason  it  is  thought  that  they 
must  be  salts  of  the  same  acid  If  we  assume  an  aluminosilicic  acid  of 
the  formula  HsAlS^Og,  albite  may  be  written  (NaSi)  AlSi2Og,  and  anor- 
thite (CaAl)AlSi20g  The  two  minerals  thus  become  salts  of  the  same 
acid  and  their  complete  isomorphism  is  explained  The  relations  that 
exist  among  many  silicates  might  be  better  understood  on  the  assump- 
tion that  they  are  salts  of  complex  silicic  and  of  aluminosilicic  acids 
than  on  the  assumption  that  they  are  salts  of  simpler  acids,  as  is  now  the 
case  But,  since  it  has  been  impossible  to  isolate  the  acids  and  study 
them  we  are  not  certain  as  to  their  character  It  is,  therefore,  believed 
best  to  represent  most  silicates  as  salts  of  the  simplest  acids  possible, 
consistent  with  their  empirical  compositions  as  determined  by  analyses 


As  in,the  case  of  salts  of  other  acids  there  are  silicates  that  contain 
hydrogen  and  oxygen  m  such  relations  to  their  other  components  that 
when  heated  they  yield  water  In  some  cases  this  water  is  driven  off  at 
a  comparatively  low  temperature  and  the  residue  of  the  compound  re- 
mams  unchanged  A  compound  of  this  kind  is  usually  called  a  hydrate 
or  the  compound  is  said  to  contain  water  of  crystallization  In  other 
cases  a  high  temperature  is  necessary  to  drive  off  water,  and  the  com- 
pound breaks  up  into  simpler  ones  In  these  instances  the  water  is 
said  to  be  combined  The  compound  is  usually  basic 

In  the  descriptions  of  the  silicates  the  order  in  which  the  minerals  are 
discussed  is  that  of  increasing  acidity,  i  e  ,  increasing  proportion  of  the 
Si02  group  present  m  the  molecule  This  order,  however,  is  not  fol- 
lowed ngorously  The  members  of  well  defined  groups  of  closely  related 
minerals  are  discussed  together  even  if  their  acidity  varies  widely 
Nearly  all  the  silicates  are  transparent  or  translucent  and  all  are  elec- 
trical insulators 


OLIVINE  GROUP  (R"aSi04)     R"=Mg,  Fe,  Mn,  Zn 

The  members  of  the  olivine  group  are  normal  silicates  of  the  metals 
Mg,  Fe,  Mn  and  Zn  They  constitute  an  isomorphous  series  crystalliz- 
ing in  the  holohedral  division  of  the  orthorhombic  system  (rhombic  bi- 
pyramidal  class)  The  most  common  member  is  the  magnesium-iron 
compound  (Mg  Fe)2Si04,  ohmne,  or  thrysot  Ic,  from  which  the  group 
gets  its  name.  The  members  with  the  simplest  composition  are  for- 
st&rite  (Mg2Si04),  fayahte  (FeaSiO^  and  tephrotte  (Mn2SiOj.)  The 
others  are  isomorphous  mixtures  of  these,  with  the  exception  of  three 
rare  minerals,  of  which  one,  monttcelhte,  is  a  calcium  magnesium  silicate, 
another,  tttanohwne,  contains  Ti  in  place  of  a  part  of  the  Si,  and  the 
other,  roeppente,  contains  some  Zn2Si04  Most  of  them  are  formed 
by  crystallization  from  molten  magmas 

Crystals  of  all  the  members  of  the  group  are  prismatic  and  all  have 
nearly  the  same  habit  They  are  often  flattened  parallel  to  one  of  the 
pinacoids,  oo  P  56  (oio)  or  oo  P  55  (100)  The  axial  ratios  of  the  com- 
moner members  are  as  follows 

Forstente  a  :  b  .  c=  4666  :  i  :  5868  The  angle  iioAiTo=$o°  2' 

Ohvine  =  4658    i  :  5865  The  angle  no  A  110=49°  57' 

Tephroite  =  4600  .  i  :  5939  The  angle  no  A  110=49°  24' 

Fayahte  =  4584  :  i  :  5793  The  angle  iioAiTo=49° 




Crystals  of  olivine  are  usually  combinations  of  some  or  all  of  the  following 
forms-      oo  P  56  (100),     oo  P  06  (oio), 
oP(ooi),        ooP(no),       ooP2(i2o), 

Po6  (Oil),        2Po6(o2l),        Poo(lOl), 

P(ni)  and  2P2(i2i)  (Fig.  163) 
The  crystals  of  fayahte  are  usually 
more  tabular  than  those  of  olivine, 
but  forsterite  and  tephroite  crystals 
have  nearly  the  same  forms  The 
cleavage  of  all  is  distinct  parallel 
to  oo  P  66  (oio),  less  distinct  parallel 
to  oo  P  oo  (100)  in  olivine,  and  par- 
allel to  oP(ooi)  in  fayahte 

The  compositions  of  the  pure  Mg, 
Mn,  and  Fe  molecules  are 


163—  Olivine    Crystals    with 
ooP,  no  (m)t     oop  So,  oio  (b), 

OP,  001  (c),    2P5,02l(&),    00  PI, 

120  ($),P  oo  ,  ioi  (d)  and  P,  in  (e) 


Mg2Si04       Mn2Si04 

57  i 

70  25 

42  9 

29  75 


70  6 
29  4 

All  natural  crystals,  however,  contain  some  of  all  the  metals  indicated 
and,  in  addition,  many  specimens  contain  also  a  determmable  quantity 
of  CaO  and  traces  of  other  elements 

Forsterite,  Olivine  and  Fayalite  (MfeSiO*  -  (Mg  Fe)2Si04  -Fe2Si04) 

The  composition  of  olivine  naturally  depends  upon  the  proportion 
of  the  forsterite  and  fayahte  molecules  present  in  it  When  the  propor- 
tion of  FeO  exceeds  24  per  cent,  the  variety  is  known  as  hya^derite 
A  few  typical  analyses  are  quoted  below 




I  51  64 

S  °i 

r  08 

II   50  27 


III    48   12 

ii  18 


IV  39  68 

22  54 

A1203       Si02 

42       42  30 

41  19 

40  39 

37  17 

Total        Sp  Gr 
100  45         3  261 


99  81          3.294 
99  39 

I   From  masses  enclosed  m  Vesuvian  lava 
II  Concretion  in  basalt  near  Sasbach,  Kaiserstuhl 

III  Grams  from  glacial  debris,  Jan  Mayen,  Greenland 

IV  Grams  from  coarse-grained  rock,  near  Montreal,  Canada 


In  addition,  there  are  often  also  present  small  quantities  of  Ni,  Mn, 
and  Ti 

Forsterite,  olivme  and  fayalite  are  usually  yellow  or  green  in  color 
and  have  a  vitreous  luster.  Forsterite  is  sometimes  white  and  ohvine 
often  brown.  All  three  minerals  become  brown  or  black  on  exposure 
to  the  air  All  are  transparent  or  translucent  Their  streak  is  colorless 
or  yellow  The  fracture  of  ohvine  is  conchoidal  In  the  other  two 
minerals  it  is  uneven  Their  hardness,  density  and  refractive  indices 
for  yellow  light  are  as  follows 

Hardness      Sp  Gr  a.  ft  7 

Forsterite                 6-7      3  21-3  33  i  6319  i  6519  i  6698 

Olivme.                6  5-7      3  27-3  37  i  6674  i  6862  i  7053 

Fayalite                   65      4  00-4  14  i  8236  i  8642  i  8736 

Before  the  blowpipe  most  olivines  and  forsterites  whiten  but  are  in- 
fusible Their  fusion  temperatures  are  between  1300°  and  1450°, 
decreasing  with  increase  in  iron  Fayahte  and  varieties  of  ohvine  rich 
in  iron  fuse  to  a  black  magnetic  globule  All  three  minerals  are  decom- 
posed by  hydrochloric  and  sulphuric  acids  with  the  separation  of  gelat- 
inous silica ,  the  iron-rich  vaneties  are  decomposed  more  easily  than 
those  poor  m  iron 

The  minerals  are  characterized  by  their  color  and  solubility  m 

Both  fayalite  and  ohvine  alter  on  exposure  to  the  air,  the  former 
changing  to  an  opaque  mixture  of  Fe20s  and  Si02,  or  to  the  fibrous 
mineral  anthophylhte  ((Mg-Fe)SiOs),  and  ohvine  to  a  mixture  of 
iron  oxides  and  fibrous  or  scaly  gray  or  green  serpentine  (BUMgaS^Oo). 
In  other  cases,  under  metamorphic  conditions,  the  alteration  is  to  a 
red  lamellar  mineral  (iddingsite)  which  may  be  a  form  of  serpentine, 
or  to  magnesite,  or  to  the  silicate,  talc  Other  kinds  of  alteration  of 
this  mineral  have  also  been  noted  but  those  descnbed  are  the  most 

Syntheses — The  members  of  the  ohvine  series  have  been  produced 
by  fusing  together  the  proper  constituents  in  the  presence  of  magnesium 
and  other  chlorides  They  are,  moreover,  present  in  many  furnace 
slags  where  they  have  been  made  in  the  process  of  ore  smelting. 

Occurrence  — Ohvine  occurs  as  an  original  constituent  of  basic  igneous 
rocks  and  as  a  metamorphic  product  m  dolomitic  limestones  It  is 
found  also  in  the  form  of  rounded  grains  in  some  meteoric  irons.  Fayalite 
occurs  in  acid  igneous  rocks,  especially  where  affected  by  pneumatolytic 


action,  and  forsterite  in  dolomitic  rocks  \\hen  they  have  been  meta- 
morphosed by  the  action  of  igneous  rocks 

Local^t^es  — Members  of  the  olivine  group  occur  m  the  basaltic  lavas 
of  many  volcanoes — as  those  of  the  Sandwich  Islands,  in  the  limestone 
inclusions  in  the  lava  of  Mt  Somma,  near  Naples;  in  vanous  basic 
rocks  in  Vermont  and  New  Hampshire  and  at  Webster,  N  C.  At  the 
latter  place  granular  aggregates  of  almost  pure  ohvme  constitute  great 
rock  masses  known  as  dunite 

Fayalite  is  found  in  the  rhyohtes  of  Mexico,  the  Yellowstone  Park 
and  elsewhere,  and  in  coarse  granite  at  Rockport,  Mass ,  and  in  the 
Mourne  Mountains,  Ireland 

Forstente  occurs  in  limestone  enclosures  in  the  lava  of  Mt  Somma 
and  at  limestone  contacts  with  igneous  rocks  at  Bolton,  Roxbury,  and 
Littleton,  Mass ,  and  elsewhere. 

Uses  and  Production.— The  only  member  of  the  group  that  is  of  any 
economic  importance  is  a  pale  yellowish  green  transparent  ohvine,  which 
is  used  as  jewelry  under  the  name  of  "  peridot  "  Gem  material  is  found 
at  Fort  Defiance  and  Rice,  in  Arizona,  scattered  loose  in  the  soil  The 
little  grams  came  from  a  basic  volcanic  rock.  The  amount  produced  in 
the  United  States  during  1912  was  valued  at  about  $8,100. 

Tephroite  (Mn2Si04) 

Although  tephroite  is  regarded  as  the  manganese  silicate  it  nearly 
always  contains  some  of  the  forsterite  molecule 

Analyses  of  brown  (I),  and  red  (II),  varieties  from  Sterling  Hill 

MnO        FeO     MgO       CaO      ZnO       Loss       SiOs       Total 

I  52  3*        i  52        7  73      *  fc>      5  93          28        30  55        99  93 

II  47  62  23      14  03         S4      4  77         35        3*  73        99  2  7 

The  mineral  is  gray,  brown  or  rose-colored  and  transparent  or 
translucent  Its  streak  is  nearly  colorless  It  is  rarely  found  m  crys- 
tals Its  hardness  is  about  6  and  its  density  408  It  is  strongly 
pleochroic  in  reddish,  brownish  red  and  greenish  blue  tints  Its  inter- 
mediate refractive  index  for  yellow  light = about  i  80. 

It  is  fusible  with  difficulty  (fusing  temperature  =1200°),  and  is  sol- 
uble in  HC1  with  separation  of  gelatinous  silica  It  is  distinguishable 
from  other  like-appearing  minerals  by  its  difficult  fusibility  and  its 
reaction  with  HC1 

Syntheses  — Crystals  of  the  mineral  have  been  made  by  fusing  to- 
gether Si02  and  Mn02  in  the  proportion  of  i  :  2,  and  by  long-continued 


heating  of  MnCb  and  Si02  in  an  atmosphere  of  moist  hydrogen  or  carbon 

Localities  — -Tephroite  occurs  at  Mine  Hill  and  Sterling  Hill,  near 
Franklin,  N  J ,  where  it  is  associated  with  franldmite,  zmcite  and 
troostite  It  is  found  also  at  Pajsberg  in  Sweden  with  other  man- 
ganese minerals  and  magnetite,  and  at  Langban,  in  Wermland, 

Uses — The  mineral  is  of  little  commercial  value  It  is  separated 
with  other  manganese  minerals  from  the  zinc  ore  of  Franklin,  N.  J  ,  and 
is  smelted  with  these  in  the  production  of  spiegeleisen, 


The  willemite  group  comprises  the  two  minerals  willemite  (Z^SiO*) 
and  troostite  ((Zn  Mn)2SiC>4),  of  which  the  latter  is  rare  Willemite 
occurs  in  small  quantity  only,  but  troostite  is  an  important  source  of 
zinc  at  the  Franklin  locality  in  New  Jersey  Both  minerals  are  found  in 

Willemite  and  troostite  crystallize  m  the  rhombohedral  hemihedral 
division  of  the  hexagonal  system  (ditrigonal  scalenohedral  class),  with 
the  axial  ratios 

Willemite   a  ;  c=  i :  o  6698 
Troostite  =  i  .  0.6698 

Willemite  and  Troostite  (Zn2SiO4-(Zn  Mn)2SiO4) 

Willemite  and  troostite  occur  massive,  in  grains,  and  m  simple  crys- 

The  theoretical  composition  of  willemite  is  8102—2704  and  ZnO 
=  72  96,  but  nearly  all  natural  crystals  contain  traces  of  other  elements 
When  a  noticeable  quantity  of  manganese  is  present,  the  compound 
is  troostite  Several  analyses  are  quoted  below 

Si02  ZnO  MnO  FeO  Total 

Willemite  from  Stolberg,  Germany             26  90  72  91  35  100  16 

Willemite  from  Greenland                         27  86  71  51  .  37  99  74 

White  troostite  from  Franklin,  N  J           27  20  65  82  6  97  23  100  22 

Dark  red  troostite  from  Franklin,  N  J       27  14  64  38  6  30  i  24  99,00" 

The  crystals  of  willemite  exhibit  the  forms  ooR(ioTo),  oop2(ii2o), 
oR(oooi),|R(3034)  and  -|R(oil2)(Fig  164).  Twins,  with$P2(3  3  6  10) 
as  the  twinning  planes,  are  rare  The  crystals  of  troostite  are  even 
more  simple,  with  oop2(ii2o)  and  R(ioli),  usually  the  only  forms 


present,  though  -JR(oiT2),  -^(0332)  and  R3(2i3i)  are  also  occa- 
sionally found  The  angle  ion  A  1101  =  63°  59'  The  cleavage  of 
willemite  is  distinct  parallel  to  oP(oooi),  and  of  troostite  distinct 
parallel  to  ooP2(ii2o),  and  less  perfect  parallel  to  R(ioTi)  and 

Willemite  is  colorless,  yellow,  brown  or  blue     Troostite  is  green, 
yellow,  brown  or  gray     The  colored  varieties  of  both  minerals  are 
translucent     Colorless  willemite  is  transparent     Both  minerals  are 
vitreous  in  luster     Their  hardness  is  between 
5  and  6  and  density  between  3  9  and  4  3    The 
refractive  indices  of  willemite  for  yellow  light 
are     w=i  6931,  e=i  7118 

Both  minerals  glow  when  heated  before  the 
blowpipe  and  are  fused  with  difficulty  (about 
1484°),  and  both  gelatinize  with  HC1  Willem- 
ite gives  the  reaction  for  zinc  with  Co(NOa)2 
on  charcoal,  and  troostite  gives,  in  addition, 
the  reaction  for  manganese.  FIG  164— Willemite  Ciys- 

Syntkeses— Willemite  crystals    have  been'     td  with -Pa,  XMO  (c), 

made   by  the    action  of    gaseous  hydrofluo-  W  and  ~ 

silicic  acid  upon  zinc,  and  by  the  action  of 

silicon  fluoride  on  zmc  oxide  at  cherry-red  temperature 

Localities  and  Origin  — Willemite  occurs  in  comparatively  small  quan- 
tity at  only  a  few  places,  associated  with  other  zinc  minerals.  In 
America  it  is  found  in  colorless  and  black  crystals  at  the  Merritt 
Mine  near  Socorro,  New  Mexico,  associated  with  mimetite,  wulfenite, 
cerussite,  bante  and  quartz 

Troostite  occurs  only  at  Sterling  Hill  and  Franklin  Furnace,  N  J , 
but  in  such  large  quantity  that  it  constitutes  an  important  proportion 
of  the  zmc  ore  for  which  these  localities  are  noted  It  is  associated  with 
franklmite  and  zincite.  Both  willemite  and  troostite  are  results  of 
magmatic  processes. 

Phenacite  (Be2Si(>4) 

The  theoretical  composition  of  the  compound  B^SiO*  is  SiO4=  54  47, 
BeO=45  S3  Many  of  the  analyses  of  phenacite  show  that  it  ap- 
proaches very  closely  to  this.  A  specimen  from  Durango,  Mexico,  for 
example,  is: 

SiO=  54  71,  BeO=45  32,  MgO+CaO=  14-    Total- 100 17. 


Phenacite  crystallizes  in  the  rhombohedral  tetartohedral  division  of 
the  hexagonal  system  with  a  :  c=  i  i  0661  It  occuis  m  crystals  pos- 
sessing many  different  types  of  habit  and  with  many  different  combina- 
tions of  forms  Perhaps  oop2(ii2o),  ooP(ioTo),  R(ioTi),  R3(2i3i) 
and  — |R(oil2)  are  the  most  common  (Fig  165)  Interpenetration 

twins  are  common  at  some  localities  The 
cleavage  is  indistinct  parallel  to  oo  P(ioTo) 
The  angle  loTi  A^IOI  =  63°  24' 

Phenacite  is  colorless  or  white  or  some 
light  shade  of  yellow  or  pink.  It  is  trans- 
parent or  translucent  and  has  a  glassy  luster 
Its  hardness  is  7  5,  and  density  about  3  and 
the  refractive  indices  for  yellow  light  are 

FIG    ^-Phenacnte  Crystal  «-' «54*,   -i  6700       It'a  infusible  and 

with  oo  p2,  1 1 20  (a),  OOP,  insoluble  in  acids     When  heated  with  a 

-IPs    -  -  little  soda  before  the  blowpipe  it  affords  a 

ioTo  (m)  and  -j-r,  1322  ^^  ^^^      ^  ^^j  ^  phosphores_ 

cent  and  pyroelectric 

Colorless  phenacite  resembles  quartz  and  Jerdente,  and  the  yellow 
vanety  topaz  It  is  best  distinguished  from  them  by  its  crystalliza- 

Syntheses  — Small  crystals  have  been  made  by  the  fusion  of  a  mix- 
ture of  Si02  and  beryllium  oxide  and  borax,  and  by  melting  together 
beryllium  nitrate,  silica  and  ammonium  nitrate 

Localities. — Phenacite  occurs  at  the  Emerald  Mines  near  Ekaterin- 
burg in  the  Urals,  near  Fremont,  in  the  Vogesen,  at  Reckmgen,  in 
Switzerland,  in  Durango,  Mexico,  near  Pike's  Peak,  at  Topaz  Butte, 
and  at  Mount  Aratero,  in  Colorado,  and  at  Greenwood,  m  Maine.  In 
all  cases  the  mineral  is  probably  a  result  of  pneumatolysis 

Uses. — The  colorless  phenacite  is  used  to  a  slight  extent  as  a  gem 

(R"3R"'2(Si04)8)     R"=Ca,  Mg,  Fe,  Mn      R'"=Al,  Fe,  Cr 

The  garnet  group  comprises  a  large  number  of  isomorphous  com- 
pounds, some  of  which  are  very  common  The  members  nearly  all 
occur  in  distinct  crystals  that  are  combinations  of  isometric  holohedrons 
(hexoctahedral  class)  Many  different  names  have  been  given  to  the 
garnets  and  analyses  show  that  they  possess  very  different  compositions 
With  the  exception  of  a  few  rare  varieties,  they  can  all,  however,  be 
explained  as  consisting  of  one  of  the  six  molecules  indicated  below,  or  of 


mixtures  of  them     The  six  molecules  and  the  names  of  the  garnets 
corresponding  to  them,  together  with  their  densities,  are. 

Caa  Ala  (8104)3    Grossulante  or  Hessomte  Sp  gr  =3  4-3  6 

Mg3Al2(Si04)3  Pyrope  =37-38 

MnaAk  (8104)3  Spessattite  ==41-43 

Almandite  =4  1-4.3 

4)3    Andradite  or  Melamte  =3  8-4  i 

3    Uvarovite  =34 

The  following  table  contains  the  calculated  percentage  composition 
of  the  several  pure  garnet  molecules  and  the  records  of  analyses  of  some 
typical  varieties  of  the  mineral 

SiOs  A12O3  FcfcOs  Cr203     FeO     MgO     CaO  MnO     TiCfe       Total 

Ia  40  01  22  69  37  30  100  oo 

Ib  42  01  17  76  5  06         13    35  01  20  100  17 

IIa  44  78  25  40  29  82  100  oo 

lib  40  92  22  45  5  46  8  ii     17  85      5  04  46                 100  39 

Ilia  36  30  20  75  .  42  95  100  oo 

Illb  36  34  12  63  4  57  47      I  49  44  20                   99  70 

IVa  36  15  20  51  43  34  100  oo 

IVb  37  61  22  70  33  83  3  61      i  44  i  12                 100  31 

Va  35  45  3i  49  33  06  100  oo 

Vb  35  09  tr  29  15  2  49         24    32  80  36                 100  48 

Vc  26  36  22  oo  i  25    30  72  tr,       21  56    101  89 

Via  38  23  29  27  29  27  100  oo 

VIb  36  93  5  68  i  96  21  84                  i  54    31  63  99  58 

Ia  Theoretical  composition  of  the  grossulante  molecule 

Ib  Green  and  red  grossulante  from  the  limestone  at  Santa  Clara,  Cal. 

IIa  Theoretical  composition  of  the  pure  pyrope  molecule 

lib  Pyrope  from  a  pendotite  in  Elliot  Co  ,  Ky     Also,  HzO  =  10. 

Ilia  Theoretical  composition  of  spessartite 

Illb  Spessartite  from  Amelia  Court  House,  Va 

IVa  Theoretical  composition  of  almandite 

IVb  Almandite  from  Sahda,  Colo 

Va  Theoretical  composition  of  andradite 

Vb  Andradite  from  East  Rock,  New  Haven,  Conn     Also,  HaO«.35. 

Vc  Schorlomite  from  Magnet  Cove,  Ark 

VIft  Theoretical  composition  of  uvarovite 

VIb  Uvarovite  from  Bissersk,  Urals 

The  crystals  of  garnet  are  usually  simple  combinations  of  oo  0(no) 
(Fig.  166);  202(211)  and  often  301(321)  (Figs  167  and  168),  although 
all  the  other  holohedrons  are  also  occasionally  met  with.  Their  cleavage 
which  is  indistinct  is  parallel  to  oo  0(no). 



When  examined  in  polarized  light  many  garnets,  especially  those 
occurring  in  metamorphic  rocks,  are  doubly  refracting  and,  therefore, 
have  not  the  molecular  structure  belonging  to  isometric  crystals  This 

FIG  166— Garnet  Crystal.    (Natural  size )    Form    ooQ  (no) 

FIG  167  FIG  168. 

FIG  167— Garnet  Crystals  with  coO,  no  (d)  and  202,  211  (»), 
FIG  168  —Garnet  Crystal  with  d  and  n  as  in  Fig  167     Also  oo  02,  210  (<?)  and  308 

231  (s)  ' 

phenomenon  has  been  explained  as  due  to  several  causes,  the  most  rea- 
sonable explanation  ascribing  it  to  strains  produced  in  the  crystals  upon 


The  garnets  vary  in  color  according  to  their  composition,  the  com- 
monest color  being  reddish  brovin  Their  luster  is  Mtreous,  their 
streak  white,  hardness  6-7  5,  and  density  3  4-4  3  They  are  transparent 
or  translucent  Most  varieties  are  easily  fusible  to  a  light  brown  or 
black  glass,  -which  in  the  case  of  the  varieties  rich  in  iron  is  magnetic 
U\  arovite,  however,  is  almost  infusible  Some  garnets  are  unattacked 
by  acids,  others  are  partially  decomposed 

Garnets,  when  in  crystals,  are  easily  distinguished  from  other  sim- 
ilarly crystallizing  substances  by  their  color  and  hardness  Massive 
garnet  may  resemble  tcsuuant'e,  spkene,  zircon  or  tzunnaine  It  is 
distinguished  from  zircon  by  its  easier  fusibility  and  from  vesuviarnte 
by  its  more  difficult  fusibility,  from  tourmaline  by  its  higher  specific 
gravity,  and  from  sphene  by  the  reaction  from  titanium 

Under  the  influence  of  the  air  and  moisture  garnets  may  be  partially 
or  entirely  changed  to  epidote,  muscovite,  chlorite,  serpentine,  and  oc- 
casionally to  other  substances 

Grossularite,  Essomte,  Hessonite,  or  Cinnamon  Garnet  occurs 
principally  in  crystalline  schists  and  in  metamorphosed  limestones, 
where  it  is  associated  with  other  calcium  silicates  It  is  found  also 
in  quartz  ve;ns  The  mineral  is  white,  bnght  yellow,  cinnamon-brown 
or  some  pale  shade  of  green  or  red.  The  lighter-colored  varieties  are 
transparent  or  nearly  so  Those  that  are  colored  are  used  as  gems 
Much  of  the  hyacvnfi  of  the  jewelers  is  a  red  grossulante  (seep  317) 
Its  hardness  is  about  7  and  its  density  3  4-3  6  It  is  fairly  easily 
fusible  before  the  blowpipe.  The  refractive  index  of  colorless  vari- 
eties for  yellow  light  is,  n=  i  7438 

Good  crystals  of  grossulante  occur  at  Phippsburg,  Raymond  and 
Rumf  ord,  in  Maine,  and  at  many  other  places  both  in  this  country  and 
abroad  Bright  yellow  varieties  are  reported  from  Canyon  City,  Colo 

Pyrope  is  deep  red,  sometimes  nearly  black.  Its  hardness  is  a  little 
greater  than  7  and  its  density  3  7  Its  refractive  index  for  yellow  light 
is  between  i  7412  and  i  7504  The  pure  magnesium  garnet  is  unknown 
All  pyropes  contain  admixtures  of  iron  and  calcium  molecules  Many 
pyropes  are  transparent  Those  with  a  dark  red  color  are  used  as  gems 
They  occur  principally  in  basic  igneous  rocks 

The  principal  occurrence  of  the  gem  variety  in  this  country  is  in 
Utah,  near  the  Arizona  line,  about  100  miles  west  of  Ganado,  Ariz , 
where  it  is  found  lying  loose  m  wind-blown  sand 

Rhodolite  is  a  pale  rose-red  or  purple  variety  from  Macon  Co.,  N  C 
It  consists  of  two  parts  pyrope  and  one  of  almandite. 


Spessartite  is  hyacinth  or  brownish  red,  with  occasionally  a  tinge 
of  violet  The  purest  varieties  are  yellow,  but  since  there  is  nearly 
always  an  admixture  of  one  of  the  iron  molecules,  the  more  usual  color 
is  reddish  brown  The  mineral  is  usually  transparent  Its  hardness  is 
7  or  a  little  greater,  and  its  density  3  77-4  27  Its  refractive  index  for 
yellow  light  is  i  8105  In  the  blowpipe  flame  it  fuses  fairly  easily  to  a 
black,  nonmagnetic  mass,  and  with  borax  gives  an  amethyst  bead  It 
is  found  in  acid  igneous  rocks  and  in  various  schists 

Its  best  known  occurrences  in  the  United  States  are  IP  granite,  at 
Haddam,  Conn ,  in  pegmatite,  at  Amelia  Court  House,  Va ,  and  in 
the  lithophyse  of  rhyohtes,  near  Nathrop,  in  Colorado 

Almandite  is  deep  red,  brownish  red  or  black  It  is  one  of  the  com- 
monest of  all  garnets  It  furnishes  nearly  all  the  material  manufactured 
into  abrasives  Transparent  vaneties  are  also  used  as  gems  The  min- 
eral has  a  hardness  of  7  and  over  Its  density  is  4  1-4  3,  and  its  refrac- 
tive index,  n,  for  yellow  light,  is  about  i  8100  It  is  slightly  decom- 
posed by  HC1  Before  the  blowpipe  it  fuses  to  a  dark  gray  or  black 
magnetic  mass  It  is  found  in  granites  and  andesites,  and  also  in  various 
gneisses  and  schists  and  in  ore  veins 

Its  best  known  occurrences  in  North  America  are  at  Yonkers  and 
at  various  points  in  the  Adirondacks,  N  Y  ,  at  Avondale,  Pa  ,  and  on  the 
Stickeen  River,  in  Alaska 

Andradite,  or  meknite,  is  black,  brown,  brownish  red,  green,  brown- 
ish yellow  or  topaz-yellow.  The  purest  varieties  are  topaz-yellow  or 
light  green  and  transparent  The  former  constitute  the  gem  topawhte 
and  the  latter,  demantwd  The  black  variety,  melamte,  nearly  always 
contains  titanium  It  occurs  m  alkaline  igneous  rocks,  in  serpentine, 
in  crystalline  schists  and  in  iron  ores  The  most  titamferous  varieties 
are  known  as  schorlomtte  The  hardness  of  andradite  is  about  7  and  its 
density  between  3  3  and  41  n  for  yellow  light  =  i  8566  It  is  fusible 
before  the  blowpipe  to  a  black  magnetic  mass 

The  mineral  is  very  widely  spread  It  occurs  at  Franklin,  N  J  ,  m 
metamorphosed  limestone,  near  Francoma,  N  H  ,  in  quartz  veins,  and 
at  many  other  places  A  black  titamferous  vanety  occurs  in  a  meta- 
morphosed limestone  in  southwestern  California  and  near  Magnet  Cove, 
m  Arkansas  The  vanety  found  at  Magnet  Cove  is  schorlormte  It  is  a 
black  glassy  mineral  associated  with  brookite  (TiCfe),  nephdme  (p  314), 
and  thomsomte  (p  455) 

Common  garnet  is  a  mixture  of  the  grossularite,  almandite  and 


andradite  molecules     It  occurs  in  many  metamorphosed  igneous  rocks 
and  in  some  slates 

Uvarovite  is  emerald-green  It  is  rare,  occurring  only  with  chromite 
in  serpentine  at  Bissersk  and  Kyschtim  in  the  Urals  and  in  the  chromite 
mines  at  Texas,  Penn  ,  and  New  Idria,  Cal  Its  hardness  is  about  7 
and  density  3  42  Its  refractive  index  for  yellow  light  is  i  8384  It  is 
infusible  before  the  blowpipe  but  dissolves  in  borax,  producing  a  green 

Syntheses  — Garnet  crystals  have  been  produced  by  fusing  9  parts  of 
nephelme  and  i  part  of  augite  (p  374)  The  fusion  results  in  a 
crystalline  mass  of  nephelme,  in  which  spinel  and  melamte  crystals  are 

Occurrence  — The  members  of  the  garnet  group  are  widely  spread  in 
nature  They  occur  in  schists,  slates  and  other  regionally  metamor- 
phosed rocks,  in  granite,  rhyohte  and  other  igneous  rocks,  and  as  con- 
tact products  in  limestones  They  are  found  also  in  quartz  veins,  in 
pegmatite,  and  associated  with  other  silicates  in  ore  veins.  In  some 
instances  they  separated  from  a  cooling  magma,  in  others  they  are  the 
products  of  pneumatohtic  process,  and  in  others  they  are  the  results  of 
contact  and  dynamic  metamorphism 

Uses  and  Production — The  varieties  that  are  transparent  are  used 
as  gems  Other  varieties  are  crushed  and  employed  as  abrasives  The 
value  of  the  gem  material  produced  in  the  United  States  in  1912  was 
$860  The  production  for  abrasive  purposes  was  4,182  short  tons,  val- 
ued at  $137,800  All  of  this  was  produced  in  the  mountain  regions  of 
New  York,  New  Hampshire  and  North  Carolina  The  rock  is  crushed 
and  the  garnet  separated  by  hand  picking,  screening,  or  by  jigging 
The  crushed  material  is  used  largely  in  the  manufacture  of  garnet  paper 


The  nephelme  group  of  minerals  includes  three  closely  related  com- 
pounds, of  which  nepheline  is  the  most  common  They  are  all  alumino- 
silicates  of  the  alkalies  Nephelme  appears  to  be  a  solution  of  Si02, 
or  of  albite,  in  isomorphous  mixtures  of  the  orthosilicates,  NaAlSiO± 
and  KAlSiO*  in  the  proportion  of  8  molecules  of  the  silicates  to  one  of 
Si02,  thus 

8(Na  K)AlSi04+Si02=(Na  K)0((Na-  K) AlSi03)2Al6(Si04)7 

The  other  two  members  of  the  group  are  eucryptite  (LiAlSKX)  and 
kdhopkOOe  (KAlSiQ*). 


The  members  of  the  group  crystallize  in  the  hexagonal  system  and 
are  apparently  holohedral,  but  nephelme  is  hemihedral  and  hemi- 
morpmc  (hexagonal  pyramidal  class)  At  temperatures  above  1,248° 
the  nephelme  molecule  crystallizes  also  in  the  trichmc  system  as  car- 
negieite  (see  p.  418), 


Although  approximately  a  potash-soda  silicate,  nearly  all  specimens 
of  nephelme  contain  more  or  less  CaO  and  nearly  all  contain  small 
quantities  of  water  All  contain  an  excess  of  SiCte  To  avoid  the 
necessity  of  assuming  the  existence  of  this  SiCb  m  solution  with 
(Na  K)AlSi04,  it  has  been  suggested  that  the  variable  composition  of 
the  mineral  may  be  explained  by  regarding  it  as  a  solid  solution  of 
NaAlSisOg  and  CaAkS^Os  (best  known  in  their  trichmc  forms  as 
albite  and  anorthtte)  in  an  isomorphous  mixture  of  the  two  molecules, 
NaAlSi04  and  KAlSiO*  The  average  of  five  analyses  of  crystals  from 
Monte  Somma,  Italy,  is  shown  in  I,  and  the  composition  of  a  mass  of 
the  mineral  from  Litchfield,  Maine,  in  II 

Si02      A1203      CaO      MgO  Na20        KaO        H20         Total 

I  44  08      33  28      i  57        19      16  oo       4  76          15          100  03 

II  43  74      34  48       tr          tr       16  62        4  55          86          100  25 

When  found  in  crystals,  the  mineral  is  apparently  holohedral  in  form 
with  an  axial  ratio  i     8389     The  crystals  are  nearly  always  short 
columnar  in  habit  and  usually  consist  of  very 
simple   combinations      The  most   prominent 
forms  are  ooP(ioTo),    oop2(ii2o),  oP(oooi), 

2P(202l),    P(lo7l),    |P(loT2)    and     2P2(lI2l) 

(Fig  169)      Their  cleavage  is  imperfect  parallel 
toooP(ioIo)  and  oP(oooi) 

Nephelme  is  glassy,  white  or  gray  and  trans- 
parent, when  occurnng  as  implanted  crystals 
FIG  i69--NepheUneCrys-  The  translucent  va™*y  with   a  glassy  luster 
tal  with  oP,  oooi  (c),  *^a*  occurs  ln  rocks  is  known  as  eleohte     This 
oo  p,  iolo  (»),  P,  loir  variety  may  be  gray,  pink,  brown,  yellowish  or 
(p)  andoop2,  1120  (a)      greenish      The  streak  is  always  white      The 
fracture  of  both  forms  is  conchoidal  or  uneven; 
hardness,  5-6  and  density,  2  6     For  yellow  light,  co=  1.5424,  €=  i  5375. 


Before  the  blowpipe  nephelme  melts  to  a  \\hite  or  colorless  blebby 
glass     At  1,248°  it  passes  over  into  carnegieite  \\hich  melts  at  1,526° 
It  dissolves  in  hydrochloric  acid  with  the  production  of  gelatinous 
silica     Its  powder  before  and  after  roasting  reacts  alkaline 

The  mineral  is  distinguished  from  other  silicates  by  its  crystalliza- 
tion, gelatinization  with  acids,  and  hardness  The  massive  varieties 
are  often  distinguishable  by  their  greasy  luster 

Nephelme  alters  to  various  hydrated  compounds,  especially  to  the 
zeolites  (p.  445),  and  to  gibbsite,  muscovite,  cancnmte  and  sodahte 

Syntheses  — Nephelme  has  been  prepared  by  fusing  together  AfeOa, 
SiO2  and  Na2C03,  and  by  the  treatment  of  muscovite  by  potassium 

Occurrence  — The  mineral  occurs  principally  as  an  original  constit- 
uent of  many  igneous  rocks,  both  plutomc  and  volcanic,  and  also  as 
crystals  on  walls  of  cavities  in  them 

Locates  —Crystals  occur  near  Eberbach,  in  Baden,  in  the  inclu- 
sions within  volcanic  rocks  at  Lake  Laach,  in  Rhenish  Prussia,  in  the 
older  lavas  of  Monte  Somma,  Naples,  Italy,  at  Capo  de  Bove,  near 
Rome,  in  southern  Norway,  and  at  various  other  points  in  southern 
Europe  Massive  forms  are  found  m  coarse-brained  rocks  near  Litch- 
field,  Maine,  Red  Hill,  N  H  ,  Magnet  Cove,  Ark.,  m  the  Crazy  Mts , 
Mont ,  and  at  other  places 


Cancnmte  is  extremely  complex  in  composition  It  is  nearly  allied 
to  nephelme  but  contains  a  notable  quantity  of  C02  It  corresponds 
approximately  to  an  hydrated  admixture  of  Na2COs  and  3NaAlSi04, 
in  which  some  of  the  Na  is  replaced  by  K  and  Ca  Specimens  from 
Barkevik  (I)  in  Norway,  and  from  Litchfield  (II),  in  Maine,  yield  the 
following  analyses: 

Si02      AkOs    Fe203      CaO    Na20    K2O    C02    EfeO     Total 
I  37  01      26  42  7  19    18  36  7  27    3  12      99  37 

II.  36  29      30  12        tr.      .4  27    19  56        18    6  96    2  98    100  36 

Cancrinite  is  hexagonal  (dihexagonal  bipyramidal  class). 

Crystals  are  rare,  and  those  that  do  exist  are  very  simple,  prismatic 
forms  bounded  by   ooP(ioTo),    ooF2(ii2o),  oP(oooi)  and  P(ioTi) 
Their  axial  ratio  is  i  :  4410 


The  mineral  is  usually  found  without  crystal  planes  It  is  colorless, 
white  or  some  light  shade,  such  as  rose,  bluish  gray  or  yellow  Its 
streak  is  \vmte,  its  luster  glassy,  greasy  or  pearly  and  it  is  translucent 
Its  cleavage  is  perfect  parallel  to  ooP(ioTo)  and  less  perfect  parallel 
to  oo  P 2  1 1 20)  Its  break  is  uneven,  hardness  5  and  density  245 
For  red  light*  u>=i  5244?  *=i  49S5 

Before  the  blowpipe  the  mineral  loses  its  color,  swells  and  fuses  to  a 
colorless  blebby  glass  In  the  closed  glass  tube  it  loses  CCb  and  water, 
and  becomes  opaque  After  roasting  it  is  easily  attacked  by  weak 
acids  with  effervescence  and  the  production  of  gelatinous  silica  When 
boiled  with  water  Na2COs  is  extracted  in  sufficient  quantity  to  give  an 
alkaline  reaction 

Cancrimte  is  easily  distinguished  by  its  effervescence  with  acids  and 
the  production  of  gelatinous  silica 

Synthesis — Small  colorless,  hexagonal  crystals  with  a  composition 
corresponding  to  that  of  cancnmte,  have  been  made  by  treating  mus- 
covite  with  a  solution  of  NaOH  and  NasCOs  at  500° 

Occurrence  — The  mineral  occurs  principally  as  an  associate  of  neph- 
elme  in  certain  coarse-grained  igneous  rocks  In  some  cases  it  appears 
to  be  an  original  rock  constituent  and  in  others  an  alteration  product  of 
nephelme  It  sometimes  alters  to  natrohte  (see  p  454),  foiming  pseu- 

Localities — Cancrimte  is  found  in  rocks  at  Ditro,  Hungary,  at 
Barkevik  and  other  localities  in  southern  Norway,  where  it  occurs  m 
pegmatite  dikes,  m  the  parish  of  Kuolajarvi,  in  Finland,  and  in  nephelme 
syenite  at  Litchfield  m  Maine, 


The  orthosihcates  of  zirconium,  zircon,  and  of  thorium,  thorite,  con- 
stitute a  group,  the  members  of  which  possess  forms  that  are  almost 
identical  with  those  of  rutile,  cassitente  and  xenotime  Indeed,  parallel 
growths  of  zircon  and  xenotime  are  not  uncommon.  Formerly  zircon 
was  grouped  with  the  two  oxides. 

Zircon  and  thorite  are  tetragonal  (ditetragonal  bipyramidal  class), 
with  approximately  the  same  axial  ratios  and  the  same  pyramidal  angles. 
The  two  minerals  are  completely  isomorphous 

Zircon       ZrSiO*    a  '  c=  6391     in  A  ill  =  56°  37', 
Thorite     ThSi04          =6402  =56°  40'. 

Zircon  is  fairly  common     Thorite  is  rare. 



Zircon  (ZrSiO4) 

Zircon,  like  rutile,  is  a  fairly  common  compound  of  a  comparatively 
rare  metal  It  is  practically  the  only  ore  of  the  metal  zirconium.  It  is 
found  mainly  in  crystals  and  as  gravel 

Although  some  specimens  of  zircon  contain  a  large  number  of  ele- 
ments, others  consist  only  of  zirconium,  silicon  and  oxygen  in  propor- 
tions that  correspond  to  the  formula  ZrSiO*,  which  demands  67  2  per 
cent  ZrO  and  32  8  per  cent  SiOg 

Its  axial  ratio  is  a  :  r=i  '  6301  Its  crystals  are  usually  simple 
combinations  of  °o  P(uo)  and  P(m),  with  the  addition  of  oo  P  oo  (100) 

FIG  170 

PIG  171 

FIG.   170 — Zircon  Crystals  with  «P,   no  (w),    ooPoo,  100   (a),  3?,  331   («}, 

P,  in  (p)  andsPs,  311  (x) 
FIG  171 — Zircon  Twinned  about  P  <»  (101)     »=2P  (221) 

and  often  3P3(3ii)  (Fig  170)  Elbow  twins,  like  those  of  rutile  and 
cassitente,  are  known  (Fig  171) 

The  cleavage  of  zircon  is  very  indistinct.  Its  fracture  is  conchoidal. 
Its  hardness  is  7.5  and  density  about  4  7  The  mineral  varies  in  tint 
from  colorless,  through  yellowish  brown  to  reddish  brown  Its  streak 
is  uncolored  and  luster  adamantine  Most  varieties  are  opaque,  but 
transparent  varieties  are  not  uncommon  The  orange,  brown  and  red- 
dish transparent  kinds  constitute  the  gem  known  as  hyacinth  The 
refractive  indices  for  yellow  light  are*  o>=i  9302,  6=1,9832. 

Zircon  is  infusible,  though  colored  varieties  often  lose  their  color 
when  strongly  heated  In  the  borax  and  other  beads  the  mineral  gives 
no  preceptible  reactions.  In  fine  powder  it  is  decomposed  by  concen- 
trated sulphuric  acid.  When  fused  with  sodium  carbonate  on  platinum 
it  is  likewise  decomposed,  and  the  solution  formed  by  dissolving  the 
fused  mixture  in  dilute  hydrochloric  acid  turns  turmeric  paper  orange. 
This  is  a  characteristic  test  for  the  zirconium  salts. 


The  mineral  is  easily  recognized  by  its  hardness,  its  resistance  toward 
reagents  and  its  crystallization 

Syntheses  —Small  crystals  of  zircon  are  obtained  by  heating  for  sev- 
eral hours  in  a  steam-tight  platinum  crucible  a  mixture  of  gelatinous 
silica  and  gelatinous  zirconium  hydroxide  Crystals  have  also  been, 
made  by  heating  for  a  month  a  mixture  of  ZnCb  and  SiOa  with  6  times 
their  weight  of  lithium  bimolybdate 

Occurrence  and  Ongin  —Zircon  is  widely  spread  in  tiny  crystals  as  a 
primary  constituent  in  many  rocks,  and  in  large  crystals  in  a  few,  notably 
in  limestone  and  a  granite-like  rock  known  as  nephelme  syenite  In 
limestone  it  is  a  product  of  contact  action.  It  occurs  also  in  sands, 
more  particularly  in  those  of  gold  regions,  and  abundantly  in  a  sand- 
stone near  Ashland,  Va 

Localities  —The  principal  occurrences  of  the  mineral  are  Ceylon,  the 
home  of  the  gem  hyacinth,  the  gold  sands  of  Australia,  Arendal, 
Hakedal  and  other  places  in  Norway;  Litchfield  and  other  points  in 
Maine,  Diana,  m  Lewis  Co ,  and  a  large  number  of  other  places  in  New 
York,  at  Reading,  Penn  ,  Henderson  and  other  Counties,  m  North 
Carolina  and  Templeton,  Ottawa  Co ,  Quebec 

Uses.— Zircon  is  the  principal  source  of  the  zirconium  oxide  emplo)'ed 
in  the  manufacture  of  gauze  used  in  incandescent  gas  lights  and  in  the 
manufacture  of  cylinders  for  use  in  procuring  a  light  from  the  oxyhydro- 
gen  jet.  The  mineral  has  been  mined  for  these  purposes  in  Henderson 
Co ,  North  Carolina 

Transparent  orange-colored  zircons  are  sometimes  used  as  gems 
since  they  possess  a  high  index  of  refraction  and  consequently  have 
a  great  deal  of "  fire  "  These  are  the  true  hyacinth  The  mineral 
often  called  by  this  name  among  the  jewelers  is  a  yellowish  brown 

Production— k  small  quantity  of  zircon  is  usually  obtained  from 
Henderson  Co.,  N  C ,  but  it  rarely  amounts  to  more  than  a  few  hundred 
pounds.  The  mineral  occurs  in  a  pegmatite  and  the  soil  overlying  its 
outcrop.  It  is  obtained  by  crushing  the  rock  and  hand  picking  Usually 
there  is  a  little  also  separated  from  the  sands  in  North  Carolina  and 
South  Carolina  that  are  washed  for  monazite.  A  pegmatite  dike,  rich 
in  zircon,  is  also  bemg  prospected  in  the  Wichita  Mountains,  Okla,,  but 
no  mining  has  yet  been  attempted. 



Thorite  (ThSiO4) 

Thorite  occurs  in  simple  crystals  bounded  by  ooP(no)  and  P(in) 
(Fig  172),  and  in  masses  The  mineral  is  always 
more  or  less  hydrated,  but  this  is  believed  to  be 
due  to  partial  weathering  It  is  black  or  orange- 
yellow  (prangeite),  has  a  hardness  of  5  and  a  specific 
gravity  of  4  5-5  for  black  vaneties  and  5  2-5  4  for 
orange  varieties  Its  streak  is  brown  or  light  orange 
Hydrated  specimens  are  soluble  in  hydro  chloric  acid 
with  the  production  of  gelatinous  silica  The  min- 
eral occurs  as  a  constituent  of  the  igneous  rock, 
augite-syemte,  at  several  points  m  the  neighborhood 
of  the  Langesundfjord,  Norway, 

FIG  172  — Thonte 
Crystal  with  oc  P, 
no  (m)  and  P; 


Three  compounds  with  the  empirical  formula  AkSiOs  exist  as  min- 
erals, kyamte,  or  disthene,  andalusite  and  silhmanite.  The  first  named  is 
less  stable  with  reference  to  chemical  agents  than  the  other  two,  but  at 
high  temperatures  both  kyamte  and  andalusite  are  transformed  into 
silhmanite  Kyamte  is  regarded  as  a  metasihcate  (AlO^SiOa.  The 
other  two  are  thought  to  be  orthosilicates  (Al(A10)SiC>4)  The  latter 
are  orthorhombic  and  both  possess  nearly  equal  prismatic  angles 
They  differ  markedly,  however,  in  their  optical  and  other  physical 
properties  and,  therefore,  are  different  substances  Kyamte  is  tnchnic 
For  this  reason  and  because  of  its  different  composition  it  is  not  re- 
garded as  a  member  of  the  andalusite  group  A  fourth  mineral,  topaz, 
differs  from  andalusite  in  containing  fluorine.  Often  this  element  is 
present  in  sufficient  quantity  to  replace  all  of  the  oxygen  in  the  radical 
(A1O)  In  other  specimens  the  place  of  some  of  the  fluorine  is  taken 
by  hydroxyl  (OH).  The  general  formula  that  represents  these  varia- 
tions is  A1(A1(F  OH)2)Si04  The  mineral  crystallizes  in  forms  that  are 
very  like  those  of  andalusite,  and  if  corresponding  pyramids  are  selected 
as  groundforms  their  axial  ratios  are  nearly  alike.  Unfortunately, 
however,  different  pyramids  have  been  accepted  as  groundforms,  and 
therefore  the  similarity  of  the  crystallization  of  the  two  minerals  has 
been  somewhat  obscured  Daribunte,  another  mineral  that  crystallizes 
m  the  orthorhombic  system  with  a  habit  like  that  of  topaz  is  often  also 
placed  in  this  group,  although  it  is  a  borosilicate,  thus  CaB2  (8104)2- 



If  4P2(24i)  be  taken  as  the  groundform  of  andalusite,  3^(331)  as 
that  of  topaz  and  3?  (331)  as  that  of  danbunte,  the  corresponding  axial 
ratios  would  be 

Andalusite    a    b  .  c=  5069    i     i  4246 
Topaz  =  5281     I     *  43*3 

Danbunte  =  5445     *     *  44°2 

These,  however,  are  not  the  accepted  ratios,  since  other  and  more  prom- 
inent pyramids  have  been  selected  as  the  groundforms 

Andalusite  and  Sillimanite  (Al(AlO)SiO4) 

Andalusite  and  sillimamte  have  the  same  empirical  chemical  compo- 
sition and  crystallize  with  the  same  symmetry,  which  is  orthorhombic 
holohedral  (rhombic  bipyramidal  class),  but  they  have  different  physical 
properties  and  different  crystal  habits,  and  hence  are  regarded  as  dif- 
ferent minerals  The  theoretical  composition  of  both  is 


Total=  16000 

Nearly  all  specimens  when  analyzed  show  the  presence  of  small 

quantities  of  Fe,  Mg,  and  Ca,  but  otherwise  they  correspond  very  closely 

to  the  theoretical  composition 

Both    minerals    are  characteristic   of   metamorphosed  rocks,  but 

andalusite  occurs  principally  in  those  that  have  been  metamorphosed  by 

contact  with  igneous  mtru- 
sives,  while  Sillimanite  is 
especially  characteristic  of 
crystalline  schists  and,  in  gen- 
eral, of  rocks  that  were  dy- 
namically metamorphosed  It 
also  occurs  with  ohvme  as  in- 
clusions in  basalt  lavas  Silh- 

FIG  173— Andalusite  Crystals  with  oop,  no  mamte  is  more  stable  at  high 
(m),  oP  ooi  (c),  PS, oii  w,  cops,  TOO  temperatures  than  andalusite 

(6),    OOP  00,^010  (a),     oo  Pa,    210    (/),    f^  * 

120  (»),  Poo,  ioi  (r),  P,  in  (p)  and 

121  (*) 

When  m  contact  rocks  it  is 
found   nearer    the    intrusive 

than  andalusite 

Andalusite— The  accepted  axial  ratio  of  andalusite  is  986*1  :  i :  7024 
Its  crystals  are  columnar  in  habit  and  are  usually  simple  combinations 

Of  00  P  00  (IOO),  00  P  00  (OIO),  OP(OOI),  00  P(lio),   00  P2(2IO),   00  P2(l2o) 

Poo  (ioi),  Poo  (on)  with  sometimes  P  (in)  and  2P2(i2i)  (Fig   173). 
The  angle  no  A  110=89°  12' 


The  mineral,  when  fresh,  is  greenish  or  reddish  and  transparent 
Usually,  however,  it  is  more  or  less  altered,  and  is  opaque,  or,  at  most, 
translucent,  and  gray,  pink  or  violet  Its  cleavage  is  good  parallel  to 
oo  P(no)  and  its  fracture  uneven  Its  hardness  is  7  or  a  little  less  and 
its  density  3  1-3  2  In  some  specimens  pleochroism  is  marked,  their 
colors  being  olive-green  for  the  ray  vibrating  parallel  to  a,  oil-green  for 
that  vibrating  parallel  to  b  and  dark  red  for  that  vibrating  parallel  to  c 
For  yellow  light  the  indices  of  refraction  are  01=16326,  1(3=16390, 
7=1  6440 

Before  the  blowpipe  the  mineral  gradually  changes  to  sillimamte  and 
is  infusible  When  moistened  with  cobalt  nitrate  and  roasted  it  becomes 
blue  It  is  insoluble  in  acids 

The  mineral  is  distinguished  by  its  nearly  square  cross-section,  its 
hardness,  its  mfusibihty,  and  the  reaction  for  Al,  and  by  its  manner  of 
occurrence  in  schists  and  metamorphosed  slates 

Some  specimens  contain  as  inclusions  large  quantities  of  a  dark 
gray  or  black  material,  which  may  be  carbonaceous,  arranged  m 
such  a  way  as  to  give  a  cross-like  figure  in  cross-sections  of  crystals. 
Because  of  the  shape  of  the  figure  exhibited  by  these  crystals,  this 
variety  was  early  called  chiastohte,  and  was  valued  as  a  sacred 

Andalusite  alters  readily  to  kaolin  (p  404),  muscovite  (p  355),  and 
sillimamte  It  has  not  been  produced  artificially 

Occurrence  — Andalusite  is  found  principally  in  clay  slates  and  schists 
that  have  been  metamorphosed  by  contact  with  igneous  masses,  and 
to  a  less  extent  m  gneisses 

Localities — Its  principal  occurrences  are  in  Andalusia,  Spain,  at 
Braunsdorf,  Saxony,  at  Gefrees,  in  the  Fichtelgebirge,  in  Minas 
Geraes,  Brazil,  and  m  the  United  States  at  Standish,  Maine,  Westford, 
Mass ,  and  Litchfield,  Conn  Chiastohte  occurs  at  Lancaster  and 
Sterling,  Mass 

Use  — The  only  use  to  which  andalusite  has  been  put  is  as  a  semi- 
precious stone,  and  for  this  purpose  only  the  chiastolite  variety  is  of  any 

SiUimanite,  or  fibrokte,  occurs  principally  m  acicular  or  fibrous 
aggregates,  on  the  individuals  of  which  only  the  prismatic  forms 
ooP(no)  and  °oP|(23o)  and  the  macropmacoid  ooPw(ioo)  can  be 
detected  End  faces  are  not  sufficiently  developed  to  warrant  the 
determination  of  an  axial  ratio  The  relative  values  of  the  a  and  b 
axes  are  687  :  i.  The  angle  iioAiio*8^0. 

While  most  of  the  fibers  correspond  m  composition  very  closely  to  the 


theoretical  value  demanded  by  the  formula  Al(A10)Si04,  many  contain 
small  quantities  of  Fe20a,  MgO  and  HkO 

The  mineral  is  yellowish  gray,  greenish  gray,  olive-green  or  brownish 
It  has  a  glassy  or  greasy  luster  and  when  pure  is  transparent  Most 
specimens,  however,  are  translucent,  and  many  of  the  colored  varieties 
show  a  pleochroism  in  brown  or  reddish  tints  Its  cleavage  is  perfect 
parallel  to  oo  P  55  (100)  Its  needles  have  an  uneven  fracture  trans- 
versely to  their  long  directions  Their  streak  is  colorless,  hardness 
6-7  and  density  3  24  The  mdices  of  refraction  for  the  lighter  colored 
varieties  are  a=i  6603,  j8=  i  6612,  7—  i  6818  for  yellow  light 

Sillimanite  reacts  similarly  to  andalusite  toward  reagents  and  before 
the  blowpipe  It  is  distinguished  from  other  minerals  by  its  habit  and 
manner  of  occurrence. 

This  mineral  is  much  more  resistant  to  weathering  than  is  andalusite 
It  is,  however,  occasionally  found  altered  to  kaolin  On  the  other  hand, 
it  is  known  also  in  pseudomorphs  after  corundum 

Synthesis  —It  has  been  produced  b>  cooling  fused  silicate  solutions 
rich  in  aluminium 

Occurrence — Sillimanite  is  very  widely  spread  in  schistose  rocks, 
especially  those  that  have  been  formed  from  sediments  It  is  essentially 
a  product  of  dynamic  metamorphism,  but  is  formed  also  bv  contact 
metamorphism,  m  which  case  it  is  found  near  the  intrusive,  where  the 
temperature  was  high 

Localities  — Its  principal  occurrences  in  North  America  are  in  quartz 
veins  cutting  gneisses  at  Chester,  Conn ,  at  many  points  in  Delaware 
Co  ,  Penn ,  and  at  the  Culsagee  Mine,  Macon  Co  ,  N  C  At  the  latter 
place  and  at  Media  in  Penn ,  a  fibrous  variety  occurs  m  such  large 
masses  as  to  constitute  a  schist — known  as  fibrohte  schist. 

Topaz  (Al(Al(F-OH)2)Si04) 

Topaz  is  a  common  constituent  of  many  ore  veins  and  is  often  present 
on  the  walls  of  cracks  and  cavities  in  volcanic  rocks  It  occurs  massive 
and  also  in  distinct  and  handsome  crystals 

The  mineral  has  a  varying  composition,  which  is  explained  in  part 
by  the  fact  that  it  is  a  mixture  of  the  two  molecules  Al(AlF2)SiO4  and 
Al(Al(OH)2)SiOi  The  theoretical  composition  of  the  fluorine  molecule 
is  8102=32  6,  A1203=SS  4,  F=2o  7=108  7,  deduct  (0  =  2F)8  7 
=  loo.oo.  A  specimen  from  Florissant,  Colo  ,  gave. 

F=i6  04=106  20-6  7s(0=F)  =  99 45. 



Crystals  of  topaz  appear  to  be  orthorhombic  (rhombic  bipyramidal 
class),  but  the  fact  that  they  are  pyroelectnc  and  that  they  frequently 
exhibit  optical  phenomena  that  are  not  in  accord  with  the  symmetry  of 
orthorhombic  holohedrons  suggests  that  they  may  possess  a  lower  grade 
of  symmetry  On  the  assumption  that  the  mineral  crystallizes  with  the 
symmetry  of  orthorhombic  holohedrons  the  axial  ratio  of  fluorine  varie- 
ties is  5281  i  4771 l  With  the  increasing  presence  of  OH,  however, 
the  relative  length  of  a  increases  and  that  of  c  diminishes  The  angle 
noAiTo=55°  43'- 

The  crystals  are  usually  prismatic  in  habit  with  ooP(no)  and 
oo  P?(i2o)  predominating  They  are  notable  for  the  number  of  forms 

FIG  174  FIG  175. 

FIG  174  — Topaz  Crystals  with  oo  P,  no  (m),   oo  pT,  120  (Z),  P,  in  (u),  2P,  221  (o) 

4?  oo ,  041  00  and  oo  P  oo ,  oio  (6) 

FIG   175  — Topaz  Crystal  with  m,  I,  n  and  y  as  in  Fig   174.    Also  2?  oo ,  021  (/), 
|P  oo ,  043  (*)  and  2P  55 ,  201  (d) 

that  have  been  observed  on  them,  especially  in  the  prismatic  zone  and 
among  the  brachypyramids  The  number  of  the  latter  that  have 
already  been  identified  is  about  45 

The  three  types  of  crystals  that  are  most  common  are  shown  in 
Figs  174,  175  and  176  Their  most  prominent  forms  are  ooP(no), 
ooP2(i2o),  Poo  (on),  P(ni),  |P(223),  4?  ^(041),  oo PJ (130)  and 
oP(ooi).  Often  planes  are  absent  from  one  end  of  the  vertical  axis, 
but  since  the  etch  figures  on  the  prismatic  planes  do  not  indicate  hemi- 
morphism,  the  absence  of  the  lacking  planes  is  explained  as  being  due  to 
unequal  growth  The  planes  of  the  prismatic  zone  are  usually  striated 

The  mineral  is  colorless,  honey  yellow,  yellowish  red,  rose  and  rarely 
bluish.  When  exposed  to  the  sunlight  the  colored  varieties  fade,  and 

The  more  commonly  accepted  axial  ratio  is  a  :  6  :  c- 
£p(22i)  'being  taken  as  the  groundfonn* 

5285  :  i  :  .9539,  the  form 



fj  d,  0  and  tt  as  m  Figs  174  and  175 
Also  §P,  223  (z),  oP,  ooi  (c)  and 
4P  55  ,  401  (p) 

when  intensely  heated  some  honey-yellow  crystals  turn  rose-red  Its 
cleavage  is  perfect  parallel  to  oP(ooi)  and  imperfect  parallel  to  P  06  (on) 
and  P  oo  (101)  The  hardness  of  the  mineral  is  8  and  its  density  3  5-3  6 
Its  refractive  indices  for  yellow  light  are  a=  i  6072,  £=  i  6104, 7=  i  6176 
for  a  variety  containing  very  little  OH,  and  05=16294,  £=16308, 

7=16375  for  a  variety  rich  m 
hydroxyl  The  indices  of  refraction 
being  high,  the  mineral  when  cut 
exhibits  much  brilliancy — a  feature 
which,  together  with  its  hardness, 
gives  it  much  of  its  value  as  a 

Topaz   is  infusible   before  the 
blowpipe  and  is  insoluble  in  acids 

FIG  176— Topaz  Crystal  with  m,  I,  y,   At  a  high  temperature  it  loses  its 

fluorine  as  silicon  and  aluminium 
fluorides  The  mineral  also  ex- 
hibits pyroelectncal  properties,  but 
these  are  apparently  distributed  without  regularity  m  different 
crystals  Many  crystals  contain  inclusions  of  fluids  containing  bubbles, 
and  sometimes  of  two  immiscible  fluids  the  nature  of  which  has  not  yet 
been  determined  It  has  been  thought  that  the  principal  fluid  present 
is  liquid  carbon-dioxide  or  some  hydrocarbon 

The  mineral  is  distinguished  from  yellow  quartz  by  its  crystalliza- 
tion, its  greater  hardness  and  its  easy  cleavage 

Topaz  is  frequently  found  coated  with  a  micaceous  alteration  product 
which  may  be  steatite  (p  401),  muscovite  (p  355)  or  kaolin  (p  404) 

Synthesis  — Crystals  have  been  made  by  the  action  of  hydrofluosihcic 
acid  (EfeSiFe)  upon  a  mixture  of  silica  and  alumina  m  the  presence  of 
water  at  a  temperature  of  about  500°. 

Occurrence — The  mineral  occurs  principally  in  pegmatites,  espe- 
cially those  containing  cassitente,  in  gneisses,  and  in  acid  volcanic  rocks 
In  all  cases  it  is  probably  the  result  of  the  escape  of  fluorine-bearing 
gases  from  cooling  igneous  magmas. 

LocalMes  —Topaz  is  found  in  handsome  crystals  at  Schneckenstem 
in  Saxony,  in  a  breccia  made  up  of  fragments  of  a  tourmalme-quartz 
rock  cemented  by  topaz.  It  occurs  also  in  the  pegmatites  of  the  tin 
mines  m  Ehrenfnedersdorf,  Marienberg  and  other  places  in  Saxony, 
Bohemia,  England,  etc  ,  on  the  walls  of  cavities  in  a  coarse  granite  m 
Jekatennburg  and  the  Hmengebirge,  Russia,  in  veins  of  kaohn  cutting 
a  talc  schist  in  Mrnas  Geraes  in  Brazil;  and  in  the  cassitente-bearmg 


sands  at  San  Luis  Potosi,  Durango  and  other  points  in  Mexico  In  the 
United  States  it  occurs  on  the  walls  of  cavities  m  acid  volcanic  rocks,  at 
Nathrop,  Colo  ,  in  the  Thomas  Range,  Utah,  and  other  places  It  occurs 
also  in  veins  Tilth  muscovite,  fluonte,  diaspore  and  other  minerals  at 
Stoneham,  Maine,  and  Trumbull,  Conn 

Uses  and  Pi  oduction  — Topaz  is  used  as  a  gem  About  36  Ib  ,  valued 
at  $2,675,  was  produced  in  the  United  States  in  1911.  In  the  following 
year  the  production  was  valued  at  only  $375. 

Danburite  (CaB2(Si04)2) 

Danbunte,  which  is  a  comparatively  rare  mineral,  is  a  calcium 
borosilicate  with  the  following  theoretical  composition  8102=4884, 
B2Os  =  28  39  and  CaO=  2277  Usually,  however,  there  are  present  in  it 
small  quantities  of  AfeOs,  Fe20s,  MnaOs  and  EfeO  Thus,  crystals  from 
Russell,  New  York,  contain 

SiO2  B2O3       Al203,etc         H20        CaO        Total 

49  70          25  80  i  02  20          23  26        99  98 

The  mineral  crystallizes  in  the  orthorhombic  system  (rhombic  bipy- 
ramidal  class),  with  an  axial  ratio  5445  :  i  4801  Its  crystals  are 
usually  prismatic  in  habit  They  contain  a  great  number  of  forms,  of 
which  oo  P  &>  (100),  oo  P  06  (oio),  co  P2(i2o),  oo  P4(i4o),  and  oo  P(iio) 
among  the  prisms,  2P4(i42),  2P?(i2i)  among 
the  pyramids  and  oP(ooi)  are  the  most  prom- 
inent (Fig.  177).  The  angle  iioAiib= 
57°  8'. 

When  fresh  and  pure  the  mineral  is  trans- 
parent, colorless  or  light  yellow,  but  when 
more  or  less  impure  is  pink,  honey-yellow  or 
dark  brown  Its  streak  is  white,  and  luster 
vitreous  Its  cleavage  is  imperfect  parallel  to  JTIG  I77  —Danbunte  Cr>s- 
oP(ooi)  and  its  fracture  uneven  or  conchoidal  tal  with  oop,  no  (m), 
Its  hardness  is  about  7  and  density  2  95-3  02  °°p2,  120  (Z),  PSo ,  101 

Its  refractive  indices  for  vellow  light  are       <«,«**,*«  <r)"d4P-, 

041  (w) 
a=l  6317,  0=1  6337,  7=1  6383 

Before  the  blowpipe  the  mineral  fuses  to  a  colorless  glass  and  colors 
the  flame  green  It  is  only  slightly  attacked  by  hydrochloric  acid,  but 
after  roasting  is  decomposed  with  the  formation  of  gelatinous  silica. 
It  phosphoresces  on  heating,  glowing  with  a  red  light. 

Origin  — Danburite  is  probably  always  a  product  of  pneumatolytic 




action,  as  it  is  found  m  quartz  and  pegmatite  veins  in  the  vicinity  of 
igneous  rocks  and  on  the  walls  of  hollows  within  them 

Locahtm  —Its  principal  occurrences  in  this  country  are  at  Danbury, 
Conn  ,  where  it  is  in  a  pegmatite,  and  at  Russell,  N  Y  ,  on  the  walls  of 
rocks  and  hollows  in  a  granitic  rock  Its  principal  foreign  occurrence  is 
at  Piz  Valatscha,  in  Switzerland. 

EPIDOTE  GROUP  (CfcR'"i(OH)(Si(>4)i) 

The  epidote  group  comprises  six  substances,  of  which  two  are  di- 
morphs  with  the  composition  Ca2Al,3  (OH)  (SiO^s  =  Ca2Al2(A10H)  (SiO-Os 
One  of  these,  known  as  ztnstie,  crystallizes  in  the  orthorhombic  system, 
and  the  other,  known  as  dinozoivite,  m  the  monochiuc  system  The 
other  four  are  isomorphous  with  clmozoisite  These  are  hancockite, 
epidote,  piedmontite  and  allanite  The  composition  and  comparative 
axial  ratios  of  the  four  commoner  isomorphs  are  as  follows  (assuming 
JP(Ti2)  as  the  groundform  of  clmozoisite) 

Clmozoisite  Ca2  Ala  (OH)  (8104)3  i  4457  .  i  •  i  8057 

Epidote  Ca*(Al  Fe)8(OH)(Si04)s  15807  i  i  8057,  £=64°  36' 
Piedmontite  Ca2(Al  Mn)s  (OH)  (8104)3  i  6100  i  i  8326,  0=  64°  39' 
Allaxute  Ca2(Al  Ce  Fe)s  (OH)  (8104)3  i  SS°9  J  *  769*,  18=64°  59' 

Clmozoisite  is  rare,  though  its  molecule  occurs  abundantly  m  iso- 
morphous mixtures  with  the  corresponding  iron  molecule  m  epidote 

Zoisite  (Ca2Als(OH)(Si04)3) 

Zoisite  is  a  calcium,  aluminium  orthosilicate  containing  only  a  small 
quantity  of  the  corresponding  iron  molecule  The  theoretical  composi- 
tion of  the  pure  Ca  molecule  is 

810=3952,  Al20s=3392>   CaO=24$9,   H20=i97     Total=ioooo 

Colored  varieties  contain  a  little  iron  or  manganese  Green  crystals  (I), 
from  Ducktown,  Tenn  ,  and  red  crystals  (thvtee)  (II),  from  Kleppan,  m 
Norway,  analyze  as  follows 

Si02   A1203    Fe203  FeO    CaO  MgO  Mn203  Na20    H20    Total 

I  39  61  32  89       91      71    24  So      14  2  12    100  88 

II  42,81  31  14    2  29  18  73  i  63    i  89       64      99  13 

Zoisite  crystallizes  m  the  orthorhombic  system  (orthorhombic  bi- 
pyramidal  class),  with  the  axial  ratio  6196  :  i     3429.    Its  crystals  are 



usually  simple  and  without  end  faces  The  most  frequent  forms  are 
ooP(no),  ooP4(i4o),  oo  P  06(010)  P(in),2Pco(o2i)and4Po6(o4i) 
are  the  commonest  terminations  (Fig  178)  The  crystals  are  all  pris- 
matic and  are  striated  longitudinally  Their 
cleavage  is  perfect  parallel  to  oo  P  86  (oio) 
The  angle  no  A  110=63°  34'. 

The  mineral  is  ash-gray,  yellowish  gray, 
greenish  white,  green  or  red  in  color  and  has  a 
white  streak  The  rose-red  variety,  contain- 
ing manganese,  is  known  as  thuhte  Very 
pure  fresh  zoisite  is  transparent,  but  the  ordi- 
nary  forms  of  the  mineral  are  translucent 
Its  luster  is  glassy,  except  on  the  cleavage 
surface,  where  it  is  sometimes  pearly  Its 
fracture  is  uneven  Its  hardness  is  6  and 
density  about  33  In  specimens  from  Duck- 
town,  Tenn  ,  a=i  7002,  /3=i  7025,  7=1  7058 
for  yellow  light  A  notable  fact  in  connection  FIG  178—  Zoisite  Crystal 
with  this  mineral  is  that  with  increase  of  the  with*)?,  no(»),  ooPx, 

molecule  Ca2Fe3(OH)(Si04)3  in  the  mixture     OIOJ6)»    °°p4'  ^  «>• 

sPoo,  021  (it)  and  P,  in 



the  plane  of  its  optical  axes  tends  to  change 
from  oP(oio)  to  oo  P  06  (ooi) 

Zoisite  fuses  to  a  clear  glass  before  the  blowpipe  and  gives  off  water, 
which  causes  a  bubbling  on  the  edges  of  the  heated  fragments  It  is 
only  slightly  affected  by  acids,  but  after  heating  it  is  decomposed  by 
hydrochloric  acid  with  the  production  of  gelatinous  silica 

Occurrence— The  mineral  occurs  as  a  constituent  of  crystalline 
schists,  especially  those  rich  in  hornblende,  or  of  quartz  veins  traversing 
them  It  is  also  a  component  of  the  alteration  product  known  as 
saussitnte  which  results  from  the  decomposition  of  the  plagioclase 
(p.  418)  m  certain  basic,  augitic  rocks  known  as  gabbros  It  is  thus  a 
product  of  metamorphism 

Localities — Good  crystals  of  zoisite  are  found  near  Pregratten  in 
Tyrol,  at  Kleppan  (thuhte),  Parish  Souland,  Norway,  and  in  the  ore 
veins  at  the  copper  mines  of  Ducktown,  Tenn ,  where  it  is  associated  with 
chalcopyrite,  pynte  and  quartz. 

Epidote  (Ca2(Al-Fe)3(OH)(Si04)3) 

Epidote,  or  pistazite,  differs  from  the  monochnic  dimorph  of  zoisite 
(dmozoisite)  in  containing  an  admixture  of  the  corresponding  iron  sfli- 
cate  which  is  unknown  as  an  independent  mineral. 


Since  it  consists  of  a  mixture  of  an  aluminium  and  an  iron  compound 
its  composition  necessarily  vanes  The  four  lines  of  figures  below  give 
the  calculated  composition  of  mixtures  containing  15  per  cent,  21  per 
cent,  30  per  cent  and  40  per  cent  of  the  iron  molecule 

Per  cent 







38  60 

28  80 

6  65 

24  02 

i  93 

100  00 

38  23 

26  76 

9  32 

23  78 

i  91 

100  00 

37  67 

23  71 

13  3i 

23  43 

i  88 

100  00 

37  04 

20  32 

17  75 

23  04 

*  85 

100  00 



Most  specimens  contain  small  quantities  of  Mg,  Fe,  Mn,  Na  or  K 

Epidote  is  isomorphous  with  chnozoisite,  crystallizing  in  the  mono- 


FIG  179— Epidote  Crystals  with  °o  P 55  ,  100  (a),  oP,  001(0),  P  w ,  10!  (r),  |P  55 , 
102  (»),  PI  nI  (»)  and  P  ob ,  on  (0) 

*FiG    180 — Epidote  Crystals  with  a,  c,  r,  *,  wand  0  as  m  Fig  179     Also  oop, 
iio(w),  2PS6,  2oT(0,  -P55,  ioi  W,   -3?!,  W  (/O  and  JP5,  423  (/) 

clime  system  (monochmc  prismatic  class),  with  the  axial  ratio  i  5787  i 
:  18036.  #=64°  36'.  The  mineral  is  remarkable  for  its  handsome 
crystals,  many  of  which  are  extremely  rich  in  forms  The  crystals  are 
usually  columnar  in  consequence  of  their  elongation  parallel  to  the  b 
axis  The  most  prominent  forms  are  oo  P  56  (100),  oP(ooi),  ^P  56  (20!) 
P  w  (jol),  P(nl),  oo  P(no)  and  P  5b  (on)  (Fig,  179  and  180)  In  addi- 
tion to  these,  over  300  other  forms  have  been  identified  Twinning 
is  common,  with  oop^(ioo)  the  twinning  plane  The  angle  no  A 
ilo=  109°  56'. 

Epidote  is  yellowish  green,  pistachio  green,  dark  green,  brown  or, 
rarely,  red  It  is  transparent  or  translucent  and  strongly  pleochroic. 
In  green  varieties  the  ray  vibrating  parallel  to  the  b  axis  is  brown,  that 
vibrating  nearly  parallel  to  c,  yellow,  and  that  vibrating  perpendicular  to 


the  plane  of  these  two  is  green  Its  luster  is  glassy  and  its  streak  gray 
Its  cleavage  is  very  perfect  parallel  to  oP(ooi)  Its  hardness  is  6  5  and 
density  3  3  to  3  5  The  refractive  indices  for  yellow  light  m  a  crystal 
from  Zillerthal  are  05=17238,  /5=i  7291,  7=1  7343  They  increase 
with  the  proportion  of  the  iron  molecule  present,  being  i  7336,  i  7593 
and  i  7710  :n  a  specimen  containing  27  per  cent  of  the  iron  epidote 

The  varieties  that  have  been  given  distinct  names  are. 

BucUwidite,  a  greenish  black  variety  in  crystals  that  are  not  elon- 

Wtthanwte,  a  bright  red  variety  containing  a  little  MnO. 

Fragments  of  the  mineral  when  heated  before  the  blowpipe  yield 
water  and  fuse  to  a  dark  brown  or  black  mass  that  is  often  magnetic 
With  increase  in  iron  fusion  becomes  more  easy.  Before  fusion  epidote 
is  practically  insoluble  in  acid.  After  heating  HC1  decomposes  it  with 
the  separation  of  gelatinous  silica 

The  ordinary  forms  of  the  mineral  are  characterized  by  their  yellow- 
ish green  color,  ready  fusibility  and  crystallization 

Occurrence  and  Origin  — Epidote  occurs  in  massive  veins  cutting  crys- 
talline schists  and  igneous  rocks,  as  isolated  crystals  and  druses  on  the 
walls  of  fissures  through  almost  any  rock  and  in  any  cavities  that  may 
be  in  them,  and  as  the  pnncipal  constituent  of  the  rock  known  as  epi- 
dosite  It  is  a  common  alteration  product  of  the  feldspars  (p.  408), 
pyroxenes  (p  364),  garnet,  and  other  calcium  and  iron-bearing  minerals 
Pseudomorphs  of  epidote  after  these  minerals  are  well  known.  The 
mineral  is  a  weathering  product,  but  is  more  commonly  a  product  of 
contact  and  regional  metamorphism. 

It  has  not  been  produced  artificially 

Localities  — Epidote  crystals  are  so  widely  spread  that  only  a  few  of 
the  important  localities  in  which  they  have  been  found  can  be  mentioned 
here.  Particularly  fine  crystals  occur  m  the  Sulzbachtibal,  Salzburg, 
Austria,  in  the  Zillerthal,  in  Tyrol,  near  Zermatt,  in  Switzerland,  in 
the  Alathal,  Traversella,  Italy,  at  Arendal,  Norway,  in  Japan,  at 
Prince  of  Wales  Island,  Alaska,  and  at  many  other  points  in  North 

Piedmontite  (Ca2(Al-Mn)3(OH)(SiO4)3) 

Piedmontite  is  the  manganese  epidote,  differing  from  the  ordinary 
epidote  in  possessing  manganese  in  place  of  iron  Usually,  however, 
the  iron  and  the  manganese  molecules  are  both  present.  Typical  analy- 
ses of  crystals  from  St.  Marcel,  in  Piedmont,  Italy  (I),  Otakisan,  Japan 
(II),  and  Pine  Mt ,  near  Monterey,  Md  (III),  follow 


Si02     A1203    Mn203  MnO  Fe203  MgO   CaO    H20     Total 

I     35  68     18  93     14  27    3  22  i  34  24  32     2  24     100  oo 

II     36  16     22  52      6  43*  9  33      40    22  05     3  20     100  53* 

III     47  37     18  ss      6  85     i  92  4  02      25     15  82     2  08     100  05* 

*  II  contains  also  44  per  cent  Na2<D  The  M^Oa  contained  also  MnO 

III  contains  also  2  03  per  cent  of  the  oxides  of  rare  earths,  14  per  cent  PbO, 
ii  per  cent  CuO,  23  per  cent  Na.O  and  68  per  cent  K^O  The  specimen  contained 
also  a  little  admixed  quartz  which  was  determined  with  the  SiOj 

The  axial  ratio  of  piedmontite  is  i  6100  i  .  i  8326  18=64°  39' 
Its  crystals  are  similar  m  habit  to  those  of  epidote,  but  they  are  much 
simpler  The  most  prominent  forms  are  oo  P  60  (100),  oP(ooi),  P(In), 
£P66(To2),  ooP5b(oio)  and  ooP(no)  Twins  are  fairly  common, 
with  oo  P  56  (too)  the  twinning  plane. 

The  mineral  is  rose-red,  brownish  red  or  reddish  black  It  is  trans- 
parent or  translucent  and  strongly  pleochroic  in  yellow  and  red  tints 
and  has  a  glassy  luster  and  pink  streak  It  is  brittle,  and  has  a  good 
cleavage  parallel  to  oP(ooi)  Its  hardness  is  6  and  density  3  40.  Its 
refractive  indices  are  the  same  as  those  of  epidote. 

Before  the  blowpipe  piedmontite  melts  to  a  blebby  black  glass  and 
gives  the  manganese  reaction  in  the  borax  bead.  It  is  unattacked  by 
acids  until  after  heating,  when  it  decomposes  m  HC1  with  the  separation 
of  gelatinous  silica 

It  is  characterized  by  its  color  and  hardness  and  by  its  manganese 

Occurrence  and  Origin  —  Piedmontite  occurs  as  an  essential  constit- 
uent of  certain  schistose  rocks  that  are  known  as  piedmontite  schists 
It  occurs  also  m  veins  and  m  certain  volcanic  locks,  where  it  is  probably 
an  alteration  product  of  feldspar.  Its  methods  of  origin  are  the  same 
as  those  of  epidote 

Localities  —  Good  crystals  are  found  in  the  manganese  ore  veins  at 
St.  Marcel,  Piedmont,  on  ilmenite  in  crystalline  schists  on  the  Isle  of 
Groix,  off  the  south  coast  of  Brittany,  and  at  a  number  of  points  on  the 
Island  of  Shikoku,  Japan,  in  crystalline  schists  and  in  ore  veins  In 
the  United  States  it  is  so  abundant  m  the  acid  volcanic  rocks  of  South 
Mountain,  Penn.,  as  to  give  them  a  rose-red  color. 

Allanite  (Ca2(Al-Ce-Fe)3(OH)(SiO4)3) 

Allanite  is  a  comparatively  rare  epidote  m  which  there  are  present 
notable  quantities  of  Ce,  Y,  La,  Di,  Er  and  occasionally  other  of  the 
rarer  elements  Since  cerium  is  present  in  the  largest  quantity  the 


formula  of  the  mineral  is  usually  written  as  above,  with  the  under- 
standing that  a  portion  of  the  cenum  may  be  replaced  by  yttrium  and 
the  other  elements  Some  idea  of  the  complex  character  of" the  numeral 
may  be  gained  from  the  two  analyses  quoted  below  The  first  is  of 
crystals  from  Miask,  Ural,  and  the  second  of  a  black  massive  variety 
from  Douglas  Co ,  Colo 

I  II 

Si02  30  81  31  13 

Al20s  16  25  ii  44 

Fe2O3                                  6  29  6  24 

Ce2O3  10  13  12  50 

BeO  27 

Di203  3  43 

La203  635 
Y203  i  24 

FeO  8  14  13  59 

MnO  2  25  61 

MgO                                      13  16 

CaO  10  43  9  44 

K20                                        53  tr 

Na20  56 

H20  2  79  2  78 

C02  21 

Total  98  77  99  8r 

Allarute  rarely  occurs  in  crystals,  but  when  these  are  found  they  are 
usually  more  complex  than  those  of  piedmontite  but  much  less  compli- 
cated than  those  of  epidote.  Their  axial  ratio  is  i  5509  :  i  :  1 7691 
with  £=64°  59'  Their  habit  is  like  that  of  epidote  crystals  Common 
forms  are  ooFco(ioo),  oP(ooi),  °°P(iio)  Twins  are  like  those  of 
epidote  The  mineral  usually  occurs  as  massive,  granular  or  columnar 
aggregates,  or  as  ill-defined  columnar  crystals  resembling  rusty  nails 
It  sometimes  forms  parallel  mtergrowths  with  epidote. 

It  is  black  on  a  fresh  fracture  and  rusty  brown  on  exposed  surfaces, 
and  has  a  greenish  gray  or  brown  streak  It  has  a  glassy  luster  and  is 
translucent  in  thin  splinters,  with  greenish  gray  or  brownish  tints  and 
is  pleochroic  in  various  shades  of  brown  Its  hardness  is  5-6  and 
density  3-4,  both  varying  with  freshness  and  composition  The  cleav- 
ages are  imperfect  and  the  fracture  uneven  Its  indices  of  refraction 
are  nearly  the  same  as  those  of  epidote. 


Small  fragments  of  fresh  allanite  fuse  to  a  blebby  black  magnetic 
glass  before  the  blowpipe  and  are  decomposed  by  HC1  with  the  separa- 
tion of  gelatinous  silica 

Allamte  is  distinguished  by  its  color,  manner  of  occurrence,  and  the 
reaction  for  water  in  the  closed  tube 

The  mineral  alters  readily  on  exposure  to  the  weather,  yielding 
among  other  compounds  mica  and  hmonite 

Occurrence — Allanite  occurs  as  an  original  constituent  in  some 
granites,  and  other  coarse-grained  rocks  It  is  found  also  in  gneisses, 
occasionally  in  volcanic  rocks  and  rarely  as  a  metamorphic  mineral  in 
crystalline  limestones 

Localities — The  best  crystals  have  been  found  m  the  druses  of  a 
volcanic  rock  at  Lake  Laach,  Prussia,  in  coarse-grained  granitic  rocks 
at  several  places  in  the  Tyrol,  in  the  limestone  at  Pargas,  Finland,  and 
at  various  points  in  Ural,  Russia  Massive  allanite  occurs  in  the  coarse 
granite  veins  at  Hittero,  Norway  and  as  the  constituents  of  granites 
at  many  places  in  the  United  States  Parallel  mtergrowths  with  epidote 
are  found  in  granite  at  Ilchester,  Md 


The  chondrodite  group  of  minerals  includes  four  members  of  the 
general  formula  (Mg(F  OH^Mg^SiO^y  in  which  x  equals  i,  3,  5,  7,  and 
y,  i,  2,  3,  4  Of  these,  one  (humite)  may  be  orthorhombic  The  other 
three  are  monochmc  with  the  angle  £=90°  The  four  members  of  the 
group  with  their  compositions  and  axial  ratios  are 


Prolectite        (Mg(F  OH)2)Mg(Si04)     i  0803  •  i  •  i  8862  18=90' 
Chondrodite    (Mg(F  OH)2)Mg3(SiO4)2  i  0863    i    3  1445  £=90 

b       Z 

Humite          (Mg(F  OH)2)Mg5(Si04)3  i  0802  '1.4  4033 
Clinohumtte    (Mg(F  OH)2)Mg7(Si04)4  r  0803  •  i  •  5  6588  £=90 

To  show  the  similarity  in  the  ratios  between  the  lateral  axes  of  the 
four  minerals,  the  &  axis  of  humite  is  written  as  i  Chondrodite,  humite 
and  clmohumite  frequently  occur  together  Chondrodite  has  been 
reported  at  more  localities  than  either  humite  or  clmohumite,  but  it  is 
not  certain  that  much  of  it  is  not  chnohumite  The  three  minerals 
resemble  one  another  very  closely  They  are  relatively  unstable  under 
conditions  prevailing  at  moderate  depths  in  the  earth's  crust,  passing 
easily  into  serpentine,  brucite  or  dolomite  Only  chondrodite  is  de- 



Chondrodite  (Mg3(Mg(F-OHJ2)(Si04)2) 

Chondrodite  is  a  rather  uncommon  mineral  that  occurs  mainly  as  a 
constituent  of  metamorphosed  limestones  that  have  been  penetrated 
by  gases  and  water  emanating  from  igneous  rocks  It  is  a  characteris- 
tic contact  mineral 

Its  composition  varies  somewhat  m  consequence  of  the  fact  that  OH 
and  F  possess  the  power  to  mutually  replace  one  another  The  two 
analyses  below  are  typical  of  varieties  containing  a  maximum  amount 
of  F 

Si02          MgO        FeO        H20         F  F=0    Total 

I  33  77        57  98        3  96        *  37        5  14=102  22—2  16    100  06 
II  35  42        54  22        5  72  9  00=104  36-3  78    100  58 

I.  Crystals  from,  limestone  inclusions  in  the  lava  of  Vesuvius 
II.  Grains  separated  from  the  limestone  of  the  Tilly  Foster  Iron  Mine,  Brewster, 
N  Y 

Chondrodite  is  monoclmic  (prismatic  class),  with  an  axial  ratio 
i  0863  11:3  1445     18=90°     The  crystals  vary  widely  in  habit  and 
are    often   complex      The   forms  oP(ooi), 
oo  P  66  (100),  oo  P  oo  (oio)  and  various  unit 
and  clmohemipyramids  of  the  general  sym- 
bol x?2    are  frequently  present,  but  other 
forms  are  also  common  (Fig   181)     Twin- 
ning   about     oP(ooi)    is     also     common 
Usually,   however,  the    mineral  occurs  m 
little    rounded    grains,  in   some    instances 
showing    crystal   faces,    scattered    through  FIG  181 —Chondrodite  Crys- 
hmestone  tel  ^  °P:  ™  & »  *** » 

When  fresh,  Chondrodite  has  a  glassy  1"  ™v  2' "7  z£'  *  2' 
luster,  is  translucent  and  is  white  or  has  a  _2p*2,  121  (r4)',  — p,  ni 
light  or  dark  yellow,  brown  or  garnet  color  (j^),  p,  in  (-«2); 
It  has  a  distinct  cleavage  parallel  to  oP(ooi), 
a  conchoidal  fracture,  a  hardness  of  6  and 
a  density  of  3  15  Its  refractive  indices 
for  yellow  light  are:  01=1607,  £=1619, 
T=  i  639 

Before  the  blowpipe  Chondrodite  bleaches 

without  fusing      With  acids  it  decomposes  with  the  production  of 
gelatinous  silica 

103  to)>  jP°°7  ioi  (— &) 

and  —  P^,  ioi  (e%)  The 
a  axis  runs  from  right  to  left 
and  the  upper  left  hand 
octant  is  assumed  to  be 


It  weathers  readily  to  serpentine,  chlorite  and  brucite,  and  conse- 
quently many  grams  are  colored  dark  green  or  black 

Occurrence  —  Chondrodite,  as  has  been  stated,  occurs  in  meta- 
morphosed limestones  It  also  occurs  in  sulphide  ore  bodies  and  m  a 
few  instances  in  magnetite  deposits  It  is  probably  in  all  cases  a  pneu- 
matolytic  or  metamorphic  product 

Localities  — It  is  found  as  crystals  in  the  blocks  enclosed  m  the  lavas 
of  Vesuvius,  in  the  copper  mines  of  Kapveltorp,  Sweden,  in  limestone 
in  the  Parish  of  Pargas,  Finland,  and  at  the  Tilly  Foster  Iron  Mine,  at 
Brewster,  N  Y  It  occurs  as  grams  in  the  crystalline  limestone  of 
Sussex  Co  ,  N  J  ,  and  Orange  Co  ,  N  Y. 


The  members  of  the  datolite  group  are  four  in  number,  but 
of  these  only  two,  viz,  datohte  (Ca(B  OH)Si04)  and  gadohnite 
(Be2Fe(YO)2(Si04)2J  are  of  sufficient  importance  to  be  described  here 
Both  minerals  crystallize  similarly  in  the  monoclmic  system  ('mono- 
clinic  prismatic  class),  with  axial  ratios  that  are  nearly  alike 

Datolite      a  '  b    c—  6345     i     i  2657    ^  =  89°  51' 
Gadohmte  a    b    r=  6273     i     13215    ^  =  89° 

Datohte  (Ca(B  OH)SiO4) 

Datolite,  or  dathohte,  is  characteristically  a  vein  mineral 

The  composition  corresponding  to  the 
formula  given  above  is 

=  218$;    CaO=3Soo, 
Total  =100  oo 

Some  specimens  contain  a  little  AbO,*  and 
Fe20a  but,  m  general,  crystals  that  have 
been  analyzed  give  results  that  are  m 
close  accord  with  the  theoretical  com- 

FIG    182— Datohte  Crystal  wrth  Positlon' 

oo POO,  zoo  (a),  OOP, no  (m),  The  mineral  crystallizes  in  fine  crys- 
-Poo,  101,  (<£),  —  iPoo,  102  tals  that  are  often  very  complicated  (Fig 
(*);  -P,  in  (»),  -P3,  212  ^2)  About  115  different  forms  have 
W,  Poo,  on  (mv)  and  JPoo,  been  observed  on  ^^  Because  of  the 

012  (g) 

suppression  of  some  faces  by  irregular 

growth  many  of  the  crystals  are  columnar  in  habit,  others  are  tabular. 
Most   crystals,   however,   are   nearly   equi-dimensional      The    angle 


no /\  1 10 -64°  40'     The  mineral  occurs  also  in  globular,  radiating, 
granular  and  massi\  e  forms 

Datohte  is  colorless  or  white,  when  pure,  and  transparent  Often, 
however,  it  is  greenish,  yellow,  reddish  or  violet,  and  translucent.  Its 
streak  is  white  and  its  luster  glassy  It  has  no  distinct  cleavage  Its 
fracture  is  conchoidal  Its  hardness  is  5  and  its  sp  gr  about  3.  Some 
crystals  are  pyroelectnc  For  yellow  light,  a- 16246,  0=1.6527, 
7=1  6694 

Before  the  blowpipe  it  swells,  and  finally  melts  to  a  clear  glass  and, 
at  the  same  time,  it  colors  the  flame  green  Its  powder  before  heating 
reacts  strongly  alkaline.  After  heating  this  reaction  is  weaker.  The 
mineral  loses  water  when  strongly  heated,  and  yields  gelatinous  silica 
when  treated  with  hydrochloric  acid. 

The  mineral  is  characterized  by  its  crystallization,  its  easy  fusibility 
and  the  flame  reaction  for  boron 

Synthesis  — Datohte  has  not  been  produced  artificially. 

Occurrence,  Origin  and  Localities  — It  occurs  on  the  walls  of  clefts 
in  igneous  rocks,  in  pegmatite  veins  and  associated  with  metallic  com- 
pounds in  ore  veins.  It  is  found  in  many  ore  deposits  of  pneumatolytic 
ongin,  notably  at  Andreasberg  in  the  Harz  Mts  ,  at  Markirch,  in 
Alsace,  in  the  Seisser  Alps,  in  Tyrol,  in  the  Serra  dei  Zanchetti  in  the 
Bolognese  Apennines,  at  Arendal,  Norway,  and  at  many  other  places 
In  North  Amenca  it  occurs  at  Deerfield,  Mass  ,  at  Tariffville,  Conn  , 
at  Bergen  Hill,  N  J  ,  and  at  several  points  in  the  copper  districts  of 
the  Lake  Superior  region 

Gadolinite  (Be2Fe(YO)2(Si04)2) 

Gadolmite  is  a  rather  rare  mineral  with  a  composition  that  is  not 
well  established  Its  occurrence  is  limited  to  coarse  granite  veins  or 
dikes — pegmatites — of  which  it  is  sometimes  a  constituent. 

Its  theoretical  composition  is  as  follows,  on  the  assumption  that  it  is 
analogous  to  that  of  datolite 

810=2556,  Y203=4844,  FeO=iS32;  BeO=io68  Total=ioooo, 
but  nearly  all  specimens  contain  cermm  oxides.  Others  contain  nota- 
ble quantities  of  erbium  or  lanthanum  oxides  and  small  quantities  of 
thorium  oxide  Nearly  all  show  the  presence  of  Fe20s,  AfeOs,  CaO  and 
MgO,  and  m  some  helium  has  been  found 

The  mineral  is  found  massive  and  in  rough  crystals  with  an  axial 
ratio  a  :  b  :  c*=  6273  :  i  :  i  3215  0=89°  26^'.  The  crystals  show 
comparatively  few  forms,  of  which  ooP(no),  oP(ooi),  P£>(on), 


JPob(oi2),  P(Tn)  and  —  P(in)  are  the  most  common  The>  are 
usually  columnar  in  habit  and  are  lough  and  coarse  The  angle 
iioA  110=64°  12' 

Gadolmite  is  usually  black  or  greenish  black  and  opaque  or  trans- 
lucent, but  very  thm  splinters  of  fresh  specimens  are  translucent  or 
transparent  in  green  tints  Its  luster  is  glassy  or  resinous,  streak 
greenish  gray  and  fracture  conchoidal  Its  hardness  is  6-7  and  its 
density  about  4-4  5  Upon  heating  the  density  increases  Many  crys- 
tals appear  to  be  made  up  of  isotropic  and  amsotropic  substance,  and 
some  to  consist  entirely  of  isotropic  matter  This  phenomenon  has 
been  explained  in  a  number  of  different  ways,  but  no  one  is  entirely  satis- 
factory. In  general,  the  isotropic  material  is  believed  to  be  an  amor- 
phous alteration  form  of  the  amsotropic  variety  It  may  be  changed 
into  the  amsotropic  form  by  heating 

The  crystallized  gadolmite  swells  up  m  the  blowpipe  flame  without 
becoming  fused  and  retains  its  transparency  The  amorphous  variety 
also  swells  without  melting,  but  yields  a  grayish  green  translucent  mass 
The  mineral  phosphoresces  when  heated  to  a  temperature  between  that 
of  melting  zinc  and  silver.  After  phosphorescing  it  is  unattacked  by 
hydrochloric  acid  Before  heating  it  gelatinizes  with  the  same  reagent 
The  mineral  is  weakly  radioactive 

Localities  and,  Origin  —  Gadolmite  occurs  in  the  pegmatites  of  Ytterby 
near  Stockholm,  and  of  Fahlun,  Sweden,  on  the  Island  of  Hittero,  in 
southern  Norway,  in  the  Radauthal,  in  Harz,  at  Barringer  Hill,  Llano 
Co  ,  Texas,  as  nodular  masses  and  large  rough  crystals,  and  at  Devil's 
Head,  Douglas  Co,  Colo  In  the  last  locality  it  occurs  in  a  de- 
composed granite  as  a  black  isotropic  variety  with  a  very  complex 
composition  Specimens  analyzed  as  follows 

I  H 

Si02  22  13    21  86 

Th02  89         81 

AbOs  2  34         54 

Fe20a  i  13      3  S9 

ii  10  6  87 

(La  Di)20a            21  23  19  10 

Y20g                 .      9  50  12  63 

ErgOs      .     ,   ,.     12.74  15  80 


FeO  10  43 

BeO  7  19 

CaO  34 

H20  .                    86 

Other  60 

Total        , ,   100  48      100  02 

It  has  apparently  in  some  cases  solidified  from  an  igneous  magma. 
In  others  it  is  of  pneumatolytic  origin 



StauroUte  (Fe(AlOH)(A10)4(Si04)2) 

Staurolite  is  a  mineral  that  is  interesting  from  the  fact  that  it  fre- 
quently forms  twinned  crystals  that  resemble  a  cross  in  shape,  and  which 
consequently,  during  the  Middle  Ages,  was  held  in  great  veneration 
Its  composition  is  not  well  established  The  composition  indicated  by 
the  formula  above  is  as  shown  in  the  first  line  below  (I)  Three  analyses 
are  quoted  in  the  next  three  lines 






55  9 


2   00 

54  20 

6  83 

Q  13 

i  43 

51  16 

14  66 

2  73 

i  26 

52  92 

6  87 

7  80 

3  28 

1  59 

100  oo 
98  97 
loo  33 
100  37 

SiOo      A1203    Fe203       FeO       MgO     H20     Ti02 

I  26  3 

II   27  38 

HI   30  23 

IV   27  91 

I  Theoretical  composition 

II  From  Monte  Campione,  Switzerland 

III  From  Morbihan,  France 

IV  From  Chesterfield,  Mass 

Staurolite  crystallizes  in  the  orthorhombic  system  (bipyramidal 
class)  in  simple  crystals  with  the  axial  ratio  4734  *  i  :  6828     The  indi- 

FIG  183  FIG  184  FIG  185 

FIG  183 — Staurolite  Crystal  with  ooP,  no  (ni),    oopoo,  100  (&),  oP,  ooi  (c)  and 

P  60,101  (r) 

FIG  184  — Staurohte  Crystal  Twinned  about  |P  oo  (032) 
FIG  185  —Staurolite  Crystal  Twinned  about  |P}  (232) 

vidual  crystals  are  usually  bounded  by  oo  P(no),  oo  P  65  (ooi),  P  55  (101) 
and  often  oP(ooi),  but  all  their  faces  are  rough  (Fig  183)  The  angle 
1 10  A  i  io  =50°  40'  More  common,  however,  than  the  simple  crystals 
are  interpenetration  twins  The  most  common  of  these  are  of  two  kinds, 
(i)  with  f P  06  (032)  the  twinning  plane  (Fig  184),  and  (2)  with  |P|(232) 
the  twinning  plane  (Fig.  185)  Both  types  of  twins  yield  crosses,  but 
the  arms  of  the  first  type  are  perpendicular  to  one  another  and  those  of 


the  second  type  make  angles  of  about  60°  and  120°      Sometimes  the 
twinning  is  repeated,  giving  rise  to  trillings 

The  mineral  is  reddish  or  blackish  brown,  and  has  a  glassy  or  greasy 
luster.  Its  streak  is  white  It  is  slightly  translucent  in  fresh  crystals, 
but  usually  is  opaque  In  very  thin  pieces  it  is  pleochroic  in  hyacinth- 
red  and  golden  yellow  tints  Its  cleavage  is  distinct  parallel  to  oo  P  06 
(oio)  and  indistinct  parallel  to  ooP(no)  Its  fracture  is  conchoidal, 
its  hardness  7  and  its  density  34~38  For  yellow  light,  QJ=I  736, 
/3=i  741,  7=  i  746 

Before  the  blowpipe  staurohte  is  infusible,  unless  it  contains  man- 
ganese, in  which  case  it  fuses  to  a  black  magnetic  glass  It  is  only 
slightly  attacked  by  sulphuric  acid 

It  is  distinguished  from  other  minerals  by  its  crystallization,  m- 
fusibility  and  hardness 

Staurolite  weathers  fairly  readily  into  micaceous  minerals,  such  as 
chlorite  (p  428)  and  muscovite  (p.  355) 

Synthesis  —  It  has  not  been  produced  in  the  laboratory 

Occurrence  —  The  mineral  occurs  principal!}  m  mica  schist  and  other 
schistose  rocks  where  it  is  the  result  of  regional  or  contact  metamor- 
phism  Because  of  its  method  of  occurrence  it  frequently  contains 
numerous  mineral  inclusions,  among  them  garnet  and  mica 

Localities  —  Good  crystals  of  staurohte  are  found  in  the  schists  at 
Mte  Campione,  Switzerland,  in  the  Zillerthal,  Tyrol,  at  Aschaff  en- 
burg,  in  Bavana,  at  various  places  in  Brittany,  France,  and  in  the 
United  States,  at  Wmdham,  Maine,  at  Francoma,  N  H  ,  at  Chester- 
field, Mass  ,  in  Patrick  Co  ,  Va  ,  and  m  Fannm  Co  ,  N  C 

Uses  —  Twins  of  staurohte  are  used,  to  a  slight  extent,  as  jewelry. 
Specimens  from  Patrick  Co  ,  Virginia,  are  mounted  and  worn  as  charms 
under  the  name  of  "  Fairy  Stones." 

Dumortierite  (Al(AlO)7H(BO)(SiOi)3) 

Dumortierite  is  one  of  the  few  blue  silicates  known  It  is  a  borosili- 
cate  with  a  composition  approaching  the  formula  indicated  above  The 
analysis  of  a  sample  from  Clip,  Arizona,  gave  (I) 

SiO2     AbOs  Fe203  Ti^Oa     MgO   B203   P20r>  Lossonlgn  Total 

I.  27  99    64  49  tr        4  95      20       i  72         99  35 

II.  28  58    63  31      21      i  49  5  2i  r  53        ioo  33 

Specimens  from  California  (II)  contain  in  addition  notable  quantities 
of  TiCfe,  which  is  thought  to  exist  as  Ti203  replacing  a  part  of  the  AkOa. 


The  mineral  crystallizes  in  the  orthorhombic  s>stem  in  aggregates  of 
fibers,  needles  or  very  thin  prisms  exhibiting  only  ooP(no)  and 
oo  P  oo  (100)  without  end  faces  Its  axial  ratio  is  a  .  b=  5317  :  i,  and 
the  prismatic  angle  no  A  110=56°  Its  crystals  possess  a  distinct 
cleavage  parallel  to  oo  P  66  (100)  and  a  fracture  perpendicular  to  the 
long  axes  of  the  prisms  Twinning  is  common,  ^ith  ooP(no)  the 
twinning  plane 

Dumortierite  is  commonly  some  shade  of  blue,  but  in  some  cases  is 
green,  lavender,  white,  or  colorless  It  is  translucent  or  transparent 
and  strongly  pleochroic,  being  colorless  and  red,  purple  or  blue  Its 
streak  is  light  blue  Hardness  is  7  and  density  3  3  Its  refractive  indices 
for  yellow  light  are  a=  r  678,  /3=  i  686, 7=  i  089 

Before  the  blowpipe  the  mineral  loses  its  color  and  is  infusible.  It  is 
insoluble  m  acids 

It  is  distinguished  from  other  blue  silicates  by  its  fibrous  or  columnar 
character  and  its  insolubility  m  acids 

Its  principal  alteration  products  are  kaolin  and  damourite 
(pp  404,  357) 

Occurrence  and  Locates  — Dumortierite  occurs  only  as  a  constit- 
uent of  gneisses  and  pegmatites  It  is  found  in  pegmatite  near  Lyons, 
France,  near  Schmiedeberg,  m  Silesia,  at  Harlem,  N  Y,  in  a  granular 
quartz,  at  Clip,  Yuma  Co  ,  Ariz  ,  and  in  a  dike  rock  composed  of  quartz 
and  dumortiente,  near  Dehesa,  San  Diego  Co ,  Cal  It  is  evidently 
a  pneumatolytic  mineral  Its  common  associates  are  kyamte,  anda- 
lusite  or  sillimanite 


The  sodahte  group  includes  a  series  of  isometric  minerals  that  may  be 
regarded  as  compounds  of  silicates  with  a  sulphate,  a  sulphide  or  a  chlor- 
ide, or,  perhaps  better,  as  silicates  in  which  are  present  radicals  con- 
taining Cl,  SO4  and  S  The  minerals  comprising  the  group  are  hauymte, 
nosean,  sodalite  and  lasnnte*  Of  these,  sodahte  appears  to  be  a  mixture 
of  3NaAlSiO4  and  NaCl,  in  which  the  Cl  has  combined  with  one  atom  of 
Al,  thus  Na4(ClAl)Al2(SiC>4)3  The  other  members  of  the  group  are 
comparable  with  this  on  the  assumption  that  the  Cl  atom  is  replaced  by 
the  radicals  NaS04,  and  NaSa  It  is  possible,  however,  that  all  are 
molecular  compounds  as  indicated  by  the  second  set  of  formulas  given 
below.  All  are  essentially  sodium  salts,  except  that  in  typical  haiiynite 
a  portion  of  the  Na  is  replaced  by  Ca.  The  chemical  symbols  of  the 
four  minerals  with  the  calculated  percentages  of  silica,  alumina  and 
soda  corresponding  to  their  formulas  are: 



Si02      A1203     Na20 
37  14      31  60      25  60 

31  65      27  03       27  26 

Sodalite    Na4(Cl  •  Al)  Al2(Si04)3,  or 

3NaAlSi04  NaCl 
Noselite    Na4(NaSQi  Al)Al2(Si04)3,  01 

3NaAlSi04  Na2S04 
Hauymte  (Na2Ca)2(NaSOrAl)Ab(SiO1)3,  or    3199      2732      16.53 

3NaAlSi04  CaSO4 

Lasurxte    Na4(NaS3  Al)  A12  (8104)3,  or  31,7        26,9       27.3 

Na2S  S* 


A1)A12  (8104)3) 

Sodalite,  theoretically,  is  the  pure  sodium  compound  corresponding 
to  the  composition  indicated  by  the  formula  given  above  Natural 
crystals,  however,  usually  contain  a  little  potassium  in  place  of  some  of 
the  sodium  and  often  some  calcium,  as  indicated  by  the  analyses  of 
material  from  Montreal,  Canada  (I),  and  Litchfield,  Maine  (II),  quoted 
below  Moreover,  their  content  of  Cl  is  not  constant 

Si02    A1203  Na20  K2OCaO   Cl  C1«O  Total 

I    3752    3*38    2515     78     35    691      -      10209     -155  10054 

II    3733    3187    2456     10    .        683      =      10176*  -154  10022 

*  Includes  I  07  per  cent  H20 

Sodalite  occurs  massive  and  in  crystals  that  appear  to  be  holohedral, 
but  etch  figures  indicate  that  they  are  probably  tetrahedrally  hemi- 
hedral  (hextetrahedral  class)  Most  crystals 
are  dodecahedral  m  habit,  though  some  are 
tetrahexahedral  and  others  octahedral  The 
forms  usually  developed  are  ooO(no), 
ooQoo  (100),  0(iu),  202(112)  and  404(114). 
Interpenetration  twins  of  two  dodecahedrons 
are  common,  with  0  the  twinning  plane  (Fig 
186)  These  often  possess  an  hexagonal  habit, 
The  mineral  is  colorless,  white  or  some 
light  shade  of  blue  or  red,  and  its  streak  is 
white  Its  luster  is  vitreous  It  is  trans- 
parent, translucent  and  sometimes  opaque 
Its  cleavage  is  perfect  parallel  to  ooO(no) 

and  its  fracture  conchoidal  Its  hardness  is  5-5,6,  and  its  density 
2  3.  Its  refractive  index  for  yellow  light,  n=  14827  Some  specimens 
are  distinctly  fluorescent  and  phosphorescent. 

FIG  186— Sodalite  Inter- 
penetration  Twin  of  Two 
Dodecahedrons  Elon- 
gated in  the  Direction  of 
an  Octahedral  Axis  and 
Twinned  about  0(m) 


Before  the  blowpipe,  colored  varieties  bleach  and  all  varieties  swell 
and  fuse  readily  to  a  colorless  blebby  glass  The  mineral  dissolves  com- 
pletely in  strong  acids  and  yields  gelatinous  silica,  especially  after  heat- 
ing When  dissolved  in  dilute  nitric  acid  its  solution  yields  a  chlorine 
precipitate  with  siher  nitrate  Its  powder  becomes  bro\\n  on  treatment 
with  AgNOs,  in  consequence  of  the  production  of  AgCl 

The  mineral  is  best  distinguished  from  other  similarly  appearing 
minerals  by  the  production  of  gelatinous  silica  with  acids  and  the  reac- 
tion for  chlorine 

As  a  result  of  weathering  sodahte  loses  Cl  and  Na  and  gams  water 
Its  commonest  alteration  products  are  zeolites  (p  445),  kaolin  (p  440), 
and  muscovite  (p  355) 

Syntheses  — It  has  been  produced  artificially  by  dissolving  nepheline 
ponder  in  fused  sodium  chloride,  and  by  decomposing  muscovite 
with  sodium  hydroxide  and  NaCl  at  a  temperature  of  500°  C 

Occurrence  and  Ortgm  — Sodahte  occurs  principally  as  a  constituent 
of  igneous  rocks  rich  in  alkalies  and  as  crystals  on  the  walls  of  pores  in 
some  lavas  It  is  also  known  as  an  alteration  product  of  nephehne 

Localities  — Good  crystals  are  found  in  nepheline  syenite  at  Ditro, 
in  Hungary,  in  the  lavas  of  Mte  Somma,  Italy,  in  the  pegmatites  of 
southern  Norway;  and  at  many  other  points  where  nephehne  rocks 
occur  In  North  America  it  is  abundant  in  the  rocks  at  Brome,  near 
Montreal,  in  the  Crazy  Mts  ,  Montana,  and  at  Litchfield,  Maine  The 
material  at  the  last-named  locality  is  light  blue 

Noselite  and  Haiiymte  ((Na^CaHNaSCX  Al)Al2(Si04)3) 

Noselite,  or  nosean,  and  hauynite,  or  hauyn,  consist  of  isomorphous 
mixtures  of  sodium  and  calcium  molecules  of  the  general  formula  given 
above  Those  mixtures  containing  a  small  quantity  of  calcium  are 
usually  called  nosean,  while  those  with  larger  amounts  constitute  hauyn. 
The  theoretical  nosean  and  hauyn  molecules  are  indicated  on  p  340 
The  theoretical  compositions  of  the  pure  nosean  molecule  (I)  and  of  the 
most  common  hauyn  mixture  (II)  are  as  follows 

SiO2  A1203  Fe203  CaO  Na20  Ka20     S03  H20     Total 

I   31  65  27  03  27  26  14  06  100  oo 

II   31  99  27  32  9  94  16  53  14  22  100  oo 

HI   35  99  29  41      31  21  20  91  10  58  i  63     99  61 

IV   33  78  27  42  10  08  13  26  3  23     12  31  .    100  08 

*  Contains  also  57  per  cent  Cl 


In  line  III  is  the  analysis  of  a  blue  nosean  from  Siderao,  Cape  Verde, 
and  in  line  IV,  the  analysis  of  a  blue  haiiyn  from  the  lava  of  Monte  Vul- 
ture, near  Melfi,  Italy 

Nosean  and  hauyn  are  isomorphous  with  sodalite  They  crystallize 
is  the  isometric  system  in  simple  combinations  with  a  dodecahedral 
habit  The  principal  forms  observed  aie  ooO(no),  ooOoo(ioo) 
0002(102),  0(in)  and  202(112)  Contact  and  mterpcnetration  twins 
are  common,  with  0(m)  the  twinning  plane  The  twins  are  often 

The  minerals  have  a  glassy  or  greasy  luster,  are  transparent  or  trans- 
lucent, have  a  distinct  cleavage  parallel  to  ooQ(iio)  and  an  uneven  or 
conchoidal  fracture  Their  hardness  is  5  6  and  density  2  25  to  2  5,  the 
value  increasing  with  the  amount  of  CaO  present  Nosean  is  generally 
gray  and  hauyn  blue,  but  both  minerals  may  possess  almost  any  color, 
from  -white  through  light  green  and  blue  tints  to  black  Red  colors  are 
rare  The  streaks  of  both  minerals  are  colorless,  or  bluish  For  yel- 
low, light  #=14890  to  i  5038,  increasing  with  increase  m  the  Ca 
present  Both  minerals  are  fluorescent  and  phosphorescent. 

Before  the  blowpipe  both  minerals  fuse  with  difficulty  to  a  blebby 
white  glass,  the  blue  hauyn  retaining  its  color  until  a  high  temperature 
is  reached  In  this  respect  it  differs  from  blue  sodalite  which  bleaches 
at  comparatively  low  temperatures  Upon  treatment  with  hot  water 
both  minerals  yield  NaaS04  They  are  decomposed  with  acids  yielding 
gelatinous  silica  The  powders  of  both  minerals  react  alkaline  Both 
also  give  the  sulphur  reaction  with  soda  on  charcoal 

The  minerals  are  easily  distinguished  from  all  others  by  their  crys- 
tallization, gelatmization  with  acids  and  reaction  for  sulphur. 

Both  minerals  upon  weathering  yield  kaolin  or  zeolites  and 

Synthesis  — Crystals  of  nosehte  have  been  made  by  melting  together 
Na2C03,  kaolmite  and  a  large  excess  of  Na2SO* 

Occurrence — Hauyn  and  nosean  occur  in  many  rocks  containing 
nephehne,  especially  those  of  volcanic  origin  and  m  a  few  metamorphic 
rocks.  Hauyn  is  so  common  m  some  of  them  as  to  constitute  an  essen- 
tial component 

Localities  — Both  minerals  are  found  in  good  crystals  in  metamor- 
phosed inclusions  in  the  volcanic  rocks  of  the  Lake  Laach  region,  in 
Prussia,  also  in  the  rocks  of  the  Kaiserstuhl,  m  Baden,  in  those  of 
the  Albanian  Hills,  in  Italy,  and  at  S.  Antao  in  Cape  Verde  In 
America  haiiyn  has  been  reported  from  the  nephelme  rocks  of  the 
Crazy  Mts,,  Montana, 


Lasunte  (Na4(NaS3- Al)Al2(Si04)3) 

Lasunte  is  better  known  as  lapis  lazuli  It  is  bright  blue  in  color 
and  was  formerly  much  used  as  a  gem  stone  The  material  utilized  for 
gem  purposes  is  usually  a  mixture  of  different  minerals,  but  its  blue 
color  is  given  it  by  a  substance  with  a  composition  corresponding  to  the 
formula  indicated  above  Since  the  artificial  ultramarine,  which  is 
ground  and  used  as  a  pigment,  also  has  this  composition,  the  molecule  is 
sometimes  represented  by  the  shortened  symbol  USs,  or  if  it  contains 
but  two  atoms  of  S,  by  the  symbol  US2  The  deep  blue  lasunte  from 
Asia  contains  as  its  coloring  material  a  substance  with  a  composition 
that  may  be  represented  by  15  7  molecules  of  USs,  76  9  molecules  of 
hauyn  and  7  4  molecules  of  sodahte,  corresponding  to  the  percentages. 

SiO2  A1203  CaO  Na20  K20 

32  52  27  61  6  47  19  45  28 

S03  S  Cl  Total  (Less  C1  =  O) 

10  46  2  71  47  99  97         =  99  42 

Lasunte  is  thus  the  name  given  to  the  blue  coloring  matter  of  lapis 
lazuli,  which  is  a  mixture  It  apparently  crystallizes  in  dodecahedrons 
Its  streak  is  blue,  its  cleavage  is  dodecahedral,  its  hardness  about  5  and 
its  specific  gravity  about  2  4  Before  the  blowpipe  it  fuses  to  a  white 
glass  Its  powder  bleaches  rapidly  in  hydrochloric  acid,  decomposes 
with  the  production  of  gelatinous  silica  and  yields  H2S. 

It  is  distinguished  from  blue  sodalite  and  hauyn  by  the  reaction  with 
HC1,  especially  by  the  evolution  of  H2S 

Occurrence  — Lasunte  is  principally  a  contact  mineral  in  limestone. 

Localities  — Good  lapis  lazuli  occurs  at  the  end  of  Lake  Baikal,  in 
Siberia,  in  the  Andes  of  Ovalle,  in  Chile,  in  the  limestone  inclusions  in 
the  lavas  of  Vesuvius,  and  in  the  Albanian  Mts  ,  Italy 

Uses  — Lapis  lazuli  is  used  as  an  ornamental  stone  in  the  manufacture 
of  vases,  and  various  ornaments,  in  the  manufacture  of  mosaics,  and  as  a 
pigment,  when  ground,  under  the  name  ultramarine  Most  of  tfre  ultra- 
marine at  present  in  use,  however,  is  artificially  prepared, 

Prehaite  (H2Ca2Al2(SiO4)3) 

Prehmte  is  nearly  always  found  in  crystals,  though  it  occurs  also  in 
stalactitic  and  granular  masses 

The  theoretical  composition  of  the  pure  mineral  is  8102=43.69, 


A1203=>2478,  CaO=27i6,  and  H2O  =  437      Most  crystals,  however, 
contain  small  quantities  of  FeoOj  and  other  constituents 

SiQ.  AUOi  I'cjOj  KO  CaO  M«0  II.O      Total 

Jordansmuhl,  Silesia            44"  26  °°        Al  2<>  2°       tr  49*  10090 

Cornwall,  Penn                    4^  4Q  20  88  5  54  27  o^       ti  4  or      99  85 

Chlorastrohte,  Isle  Royale  37  41  H  02  2  21    i  81  22  20  3  46  7  72      99  75* 

*  Also   32  per  cent  Na^O 

Its  crystallization  is  orthoihomhic  and  hcraimoiphic  (rhombic  py- 
ramidal class),  with  a  b  c=  8420  i  i  1272  The  ciystals  vary 
widely  in  habit,  but  they  contain  comparatively  few  foinis  The  most 
prominent  are  oP(ooi),  ooP(uo),  6P»(o6i),  2P(32i)  and  6P(66i) 

(Fig  187)  The  angle  noAiTo=8o° 
12'  Because  they  exhibit  pyroelectnc 
l>olanty  in  the  direction  of  the  a  a.xis  the 

crvstals  arc  thought  to  be  twins,  with 
FIG   187  — Prehnite  Crystal  with         *  _  _  /       N  . ,        ,  . 

OOP/XXO  W,  OOP/,  I0o  Wl      «P»  (I*)    as    the    twinning  plane 
JP56,  304  (n),   JP55,  308  W     Cleavage  is  good  parallel  to  oP(oor) 
and  oP,  ooi  (c)  The  crystals  are  frequently  tabular 

parallel    to    oP(ooi),    although    other 

habits  are  also  common     Isolated  individuals  are  rare,  usually  many 
are  grouped  together  into  knotty  or  warty  aggregates 

Prehnite  is  colorless  or  light  green,  and  transparent  or  trans- 
lucent, and  it  has  a  colorless  streak  Its  luster  is  pearly  on  oP(ooi)  but 
glassy  on  other  faces  Its  fracture  is  uneven,  its  hardness  7+  and  its 
density  2.80-2  95.  For  yellow  light,  a=  i  616,  0=  i  626,  7  =  1  649 

Before  the  blowpipe  prehnite  exfoliates,  bleaches  and  melts  to  a 
yellowish  enamel  At  a  high  temperature  it  yields  water  Its  powder  is 
strongly  alkaline.  It  is  partially  decomposed  by  strong  hydrochloric 
acid  with  the  production  of  pulverulent  silica.  After  fusion  it  dissolves 
readily  in  this  acid  yielding  gelatinous  silica 

The  mineral  has  not  been  produced  artificially 

Occurrence — Prehnite  occurs  as  crystals  implanted  on  the  walls  of 
clefts  in  siliceous  rocks,  in  the  gas  cavities  in  lavas,  and  in  the  gangue  of 
certain  ores,  especially  copper  ores  It  is  found  also  as  pseudomorphs 
after  analcite  (p  438),  laumomte  (p  451),  and  xutrohte  (p  454)  In 
all  cases  it  is  probably  a  secondary  product  • 

Localities  — Fine  crystals  come  from  veins  at  Harzburg,  in  Thuringia, 
at  Stnegau  and  Jordansmuhl,  Silesia,  and  at  Fassa  and  other  places  in 
Tyrol.  Good  crystals  are  found  also  in  the  Campsie  Hills  in  Scotland. 
The  mineral  is  abundant  in  veins  with  copper  along  the  north  shore  of 


Lake  Superior  and  on  Keweenaw  Point,  and  it  occurs  also  at  Farmington, 
Conn  ,  Bergen  Hill,  N  J  ,  and  Cornwall,  Penn 

Uses  —  The  mineral  known  as  chlorastrolite  is  probably  an  impure 
prehnite.  It  is  found  on  the  beaches  of  Isle  Royale  and  the  north  shore 
of  Lake  Superior  as  little  pebbles  composed  of  stellar  and  radial  bunches 
of  bluish  green  fibers  The  pebbles  were  originally  the  fillings  of  gas 
cavities  in  old  lavas  The>  are  polished  and  used,  to  a  slight  extent,  as 
gem-stones  About  $2,000  worth  were  sold  in  1911  and  §350  ^orth  in 

Axinite  (H(Ca-Fe-Mn)3Al2B(SiO4)4) 

Axmite  is  especially  noteworthy  for  its  richness  in  crystal  forms 
The  mineral  is  a  complicated  borosihcate  for  ^vhich  the  formula  given 
above  is  merely  suggestive  Analyses  of  crystals  from  different  localities 
vary  so  widely  that  no  satisfactory  simple  formula  has  been  proposed 
for  the  mineral  Four  recent  analyses  are  quoted  below 

Radauthal         Stnegau  Oisans  Cornwall 

Si02  39  26  42  02  41  53  42  10 








4  gi 

£  OO 

4  62 

4  64 

14  46 

17  73 

17  90 

17  40 

2  62 


3  9° 




4  02 

5  84 

2  80 

6  52 

3  79 

4  63 

29  70 

19  21 

21  66 

20  53 

2  00 




I  22 

i  77 

2  l6 

i  80 

Total          100  62          ico  ii          100  32         100  66 

Axinite  crystallizes  in  the  trichmc  system  (pinacoidal  class),  with 
a :  b  :  c=*  4921  .  i  :  4797  and  01=82  °  54',  0=91°  52',  7=i3l0  32'- 
The  crystals  are  extremely  varied  m  habit  but  nearly  all  are  somewhat 
tabular  parallel  to  'P(iTi),  oo  P'(iio)  or  oo  'P(iTo)  About  45  forms 
have  been  observed  In  addition  to  the  three  mentioned,  2'?'  So  (201), 
P'(III),  /P(iFi),  2yP'  06  (021),  oo  P  06  (oio)  and  oo  P  oo  (100)  are  the  most 
frequently  met  with  (Figs  188,  189)  The  plane  'P(iTi)  is  usually 
striated  parallel  to  its  intersection  with  oo  'P(iTo)  The  angle  100  A  i "10 
=  15°  34'.  The  cleavage  is  indistinct  parallel  to  ooP'(no)  and  the 
crystals  are  strongly  pyro  electric 

Axinite  is  brownish,  gray,  green,  bluish  or  pink,  and  is  strongly  pleo- 
chroic  in  pearl-gray,  olive-green  and  cinnamon-brown  tints  It  is 


transparent  or  translucent  and  has  a  glassy  luster  and  a  colorless  streak 
Its  fracture  is  conchoidal  or  uneven  It  is  brittle,  has  a  hardness  of  6-7 
and  a  density  of  3  3  For  red  light,  a=  i  6720,  /3=  i  6779,  7  =  1  6810 

Axmite,  before  the  blowpipe,  exfoliates  and  fuses  to  a  dark  green 
glass  which  becomes  black  in  the  oxidizing  flame  It  colors  the  flame 
green,  especially  upon  the  addition  of  KHS04  and  CaFo  to  its  powder 
Its  powder  reacts  alkaline  It  is  only  slightly  attacked  by  acids.  After 

FIG  188  FIG  189 

FIG  188— Aximte  Crystal  with  ooPoo,  TOO  (a),   2'P'So,  201  (s),    ooP/,  no  (m), 

oo  /p  ilo  (M),  P',  m  (*)  and  'P,  ill  (r) 
FIG  189 — Axmite  Crystal  with  M ,  m,  a,  r  and  5  as  m  Fig    188     Also  ooPoo, 

oio  (6),  aP'  w  ,  021  (v),  yP,  In  (e),  |,P3,  132  (0),  4/P^,  241  (o),  3/P3,  131  (I'), 

00 /'PI.  130  (w),  3'P3,  i3i  (»)  and  4'?%  241  (<J). 

fusion,  however,  it  dissolves  readily  with  the  production  of  gelatinous 

The  mineral  is  easily  characterized  by  its  crystallization  and  the 
green  color  it  imparts  to  the  flame 

It  has  not  been  produced  artificially 

Pseudormorphs  of  chlorite  after  axroite  have  been  found  in  Dart- 
moor, England 

Occurrence  — Axmite  crystals  occur  in  cracks  in  old  siliceous  rocks. 
It  is  found  also  in  ore  veins  and  as  a  component  of  a  contact  rock  com- 
posed mainly  of  augite,  hornblende  and  quartz,  occuning  near  the 
peripheries  of  granite  and  diabase  masses.  It  was  formed  by  the  aid 
of  pneumatolytic  processes 

Localities  — Excellent  crystals  of  axmite  are  found  at  Andreasberg 
and  other  places  in  the  Harz  Mts  ,  near  Stnegau,  m  Silesia,  near 
Poloma,  in  Hungary,  at  the  Piz  Valatscha,  in  Switzerland,  near  Verms 
and  at  other  points  m  Dauphme,  France,  at  Botallak,  Cornwall,  Eng- 
land, at  Komgsberg,  Norway,  Nordmark,  Sweden;  Lake  Onega,  and 
Miask,  Russia,  at  Wales  in  Maine  and  at  South  Bethlehem,  Penn. 


Dioptase  (H2CuSiO4) 

Dioptase  is  especially  interesting  because  of  its  crystallization,  which 
is  rhombohedral  tetartohedral  (trigonal  rhombohedral  class)  Its  crys- 
tals are  columnar  Their  axial  ratio  is  i  5342  They  are  usually 

bounded  by  oo  P2(ii2o),  -  2R(o22i)  or  R(ioYi)  and  ~^i  -  (1341)  or 

jT> JL  Y          4      ^ 

H -  (3141)  (a  rhombohedron  of  the  third  order,  Fig  190)     Besides 

occurring  as  crystals  the  mineral  is  found  also 
massive  and  in  crystalline  aggregates. 

The  composition  expressed  by  the  formula 
given  above  is  8102—3818,  CuO=504o; 
H20=n  44,  which  is  approached  very  closely 
by  some  analyses.  The  same  composition  may 
be  expressed  by  CuSiOs  HaO  Indeed,  recent 
work  indicates  that  the  mineral  is  a  hydrated 
metasilicate  and  not  an  acid  orthosihcate  FIG  190  —Dioptase  Ciys- 

Dioptase  has  an  emerald-green  or  blackish      tai  Wlth  °°P2»  "20  and 
green  color,  a  glassy  luster  and  a  green  streak       ~~2R'  °221  ®>  mtl[L  a 
It  is   transparent   or   translucent,   is    brittle 
and  its  fracture  is  uneven  or  conchoidal     Its     stnations 
hardness  is  5  and  its  density  3  05.    It  is  weakly 

pleochroic  and  is  distinctly  pyroelectnc     For  yellow  light,  co=i  6580, 

Before  tie  blowpipe  dioptase  turns  black  and  colors  the  flame  green. 
On  charcoal  it  turns  black  in  the  oxidizing  flame  and  red  m  the  reducing 
flame  without  fusing  It  is  decomposed  by  acids  with  the  production  of 
gelatinous  silica 

Synthesis  — Crystals  of  dioptase  have  been  made  by  allowing  mix- 
tures of  copper  nitrate  and  potassium  silicate  to  diffuse  through  a  sheet 
of  parchment  paper 

Occurrence  and  Localities  — The  mineral  occurs  in  druses  on  quartz 
in  clefts  in  limestone,  and  in  gold-bearing  placers  in  the  Altyn-Tube  Mt. 
near  the  Altyn  Ssu  River,  m  Siberia,  in  crystals  on  wulfemte  and  cala- 
mme  and  embedded  in  clay  near  R6zbanya,  Hungary,  with  quartz  and 
chrysocolla  in  the  Mmdonli  Mine,  French  Congo,  in  copper  mines  at 
Capiapo,  Chile,  and  in  Peru,  at  the  Bon  Ton  Mines,  Graham  Co , 
Ariz  ,  and  near  Riverside,  Pinal  Co,,  in  the  same  State.  In  the  Bon 
Ton  Mines  it  covers  the  walls  of  cavities  in  the  ore,  which  consists  of  a 
mixture  of  kmomte  and  copper  oxides 




The  mica  group  comprises  a  series  of  silicates  that  are  characterized 
by  such  perfect  cleavages  that  extremely  thin  lamellae  may  be  split 
from  them  with  surfaces  that  are  perfectly  smooth.  The  lamellae  are 
elastic  and  in  this  respect  the  members  of  the  group  are  different  from 
other  minerals  that  possess  an  almost  equally  perfect  cleavage  Some 
of  the  micas  are  of  great  economic  importance,  but  most  of  them  have 
found  little  use  in  the  arts 

The  micas  may  be  divided  into  four  subgroups,  (T)  the  magnesium- 
iron  micas,  (2)  the  calcium  micas,  (3)  the  kthium-iron  micas,  and  (4) 
the  alkali  micas  Of  the  latter  there  are  three  subdivisions,  (a)  the 
lithia  micas,  (£)  the  potash  micas,  and  (c)  the  soda  micas 

All  the  micas  crystallize  in  the  monoclmic  system  (monoclmic  pris- 
matic class),  in  crystals  with  an  orthorhombic  or  hexagonal  habit 

In  composition  the  micas  are  complex  The  alkali  micas  are  ap- 
parently acid  orthosihcates  of  aluminium  and  an  alkali — the  potash 
mica  being  KHaAk  (8104)3  Other  alkali  micas  are  more  acid,  and 
some  of  the  magnesium-iron  micas  are  very  complex  The  members 
with  the  best  established  compositions  are  apparently  salts  of  orthosilicic 

acid,  and,  hence,  the  entire  group  is  placed 
with  the  orthosihcates 

All  the  micas  possess  also,  in  addition  to 
the  very  noticeable  cleavage  which  yields 
the  characteristically  thin  lamellae  that  are 
so  well  known,  other  planes  of  parting 
which  are  well  exhibited  by  the  rays  of 
the  percussion  figure  (Fig,  191)  The 
largest  ra}— known  as  the  characteristic 
ray — is  always  parallel  to  the  chnopinacoid. 
In  some  micas  the  plane  of  the  optical 
axes  is  the  chnopinacoid  and  m  others  is 
perpendicular  thereto  In  the  latter,  known 
as  micas  of  the  first  order,  the  plane  of 

the  axes  is  perpendicular  to  the  characteristic  ray  and  m  the  former, 
distinguished  as  micas  of  the  second  order,  it  is  parallel  to  this  ray. 

The  value  of  the  optical  angle  varies  widely  In  the  magnesia  micas 
it  is  between  o°  and  15°,  in  the  calcium  micas  between  100°  and  120°, 
and  in  the  other  micas  between  55°  and  75°  When  the  angle  becomes 
zero  the  mineral  is  apparently  umaxial  But  etch  figures  on  all  micas 
indicate  a  monoclmic  symmetry  (compaie  Fig  194) 

FIG  191  — Percussion  Figure 
on  Basal  Plane  of  Mica 
The  long  ray  is  parallel  to 
oo  Pob  (oio) 




Biotite  ((K  H)2(Mg  Fe)2(Al  Fe)2(Si04)3) 

The  magnesium-iron  micas  are  usually  designated  as  biotite. 
group  includes  micas  of  both  orders  as  follows 


isl  Order 

2d  Oraer 

The  crystals  of  biotite  have  an  axial  ratio   5774    i  :  3  2904  with 
$= 90°     They  are  usually  simple  combinations  of  oP(ooi),  oo  P  ob  (oio), 
•— |P(ii2)  and  P(Tn)  (Fig  192).    Twins  are 
common,  with  the  twinning  plane  perpendic- 
ular to  oP(ooi)      The  composition  face  may 
be  the  same  as  the  twinning  plane  or  it  may  be 

witu  oP,  ooi  (c),  ooPSb, 
oio  (6),  P,  In  (ju)  and 
-JP  112  (<?) 

oP(ooi)   (Fig    193)     The  crystals  have   an 

hexagonal  habit,  the  angle  IiiAoio  being  FlG^ ***~^*    ^ystel 

60°  22!'.     The  mineral  also  occurs  in  flat 

scales  and  in  scaly  aggregates 

The  color  of  biotites  varies  from  yellow, 
through  green  and  brown  to  black     Pleochroism  is  strong  in  sections 
perpendicular  to  the  perfect  cleavage,  ie,  perpendicular  to  oP(ooi) 
The  streak  of  all  varieties  is  white    Their  hardness =2.5  and  density 
27-3.1,  depending  upon  composition.     The  refractive  indices  for  yellow 

FIG.  193  — Biotite  Twinned  about  a  Plane  Perpendicular  to  oP  (ooi),  and  Parallel 
to  the  Edge  Between  oP(ooi)  and  —  aP(22i)  The  composition  plane  is 
oP(ooi)  Mica  law  A=nght  hand  twin,  B  and  C-left  hand  twins. 

light  m  a  light  brown  biotite  from  Vesuvius  are'  a— 1.5412,  /3=i  5745. 
They  are  higher  m  darker  varieties. 

Etch  figures  are  produced  by  the  action  of  hot  concentrated  sulphuric 

Varieties  and  their  Localities  — Anomite  is  rare.  It  occurs  at  Green- 
wood Furnace,  Orange  Co  ,  N»  Y.,  and  at  Lake  Baikal,  m  Siberia 


Meroxene  is  the  name  given  to  the  common  biotite  of  the  2d  order 
It  occurs  m  particularly  fine  crystals  in  the  limestone  blocks  included 
in  the  lava  of  Mte  Somma,  Naples,  Italy,  at  various  points  in  Switzer- 
land, Austria  and  Hungary,  and  at  many  other  points  abroad  and  in 
this  country 

Lepidomelane  is  a  black  meroxene  characterized  by  the  presence 
in  it  of  large  quantities  of  ferric  iron  It  is  essentially  a  magnesium-free 
biotite  It  occurs  in  igneous  rocks,  especially  those  rich  in  alkalies 
Two  of  its  best  known  occurrences  in  the  United  States  are  in  the  nephe- 
hne  syenite  at  Litchfield,  Maine,  and  in  a  pegmatite  in  the  northern  part 
of  Baltimore,  Md 

Phlogopite,  or  amber  mica,  is  the  nearly  pure  magnesium  biotite 
which  by  most  mineralogists  is  regarded  as  a  distinct  mineral,  partly 
because  m  nearly  all  cases  it  contains  fluorine  Its  color  is  yellowish 
brown,  brownish  red,  brownish  yellow,  green  or  white  Its  luster  is 
often  pearly,  and  it  frequently  exhibits  astensm  in  consequence  of  the 
presence  of  inclusions  of  acicular  crystals  of  rutile  or  tourmaline  arranged 
along  the  rays  of  the  pressure  figure  Its  axial  angle  is  small,  increasing 
with  increase  of  iron  Its  refractive  indices  are  a=i  562,  £=i  606, 
7=1  606 

Phlogopite  is  especially  characteristic  of  metamorphosed  limestones 
It  occurs  abundantly  in  the  metamorphosed  limestones  around  Easton, 
Pa  ,  at  Edwards,  St  Lawrence  Co  ,  N  Y  ,  and  at  South  Burgess, 
Ontario,  Canada.  It  is  also  found  as  a  pyrogenetic  mineral  in  certain 
basic  igneous  rocks, 

Typical  analyses  of  the  four  varieties  of  biotite  follow. 






40  81 

35  79 

32  35 

39  66 

3  5i 



16  47 

13  70 

17  47 

17  co 

2  16 

4  04 

24  22 


s  92 

17  09 

13  II 



I.  2O 



CaO  i  48 

BaO  33  62 

MgO  21  08  9  68  89  26  49 

Na20  i  55  45  7  oo  60 


I  II               III  IV 

K20                 9  01  8  20            6  40  9  97 

H20-           \  90  I      ,  66 

H20+           I219  3*6  I*6'  233 

F  10  2  24 

(lessO=F)  99  19  99  91         100  83  99  66 

I  Anomite  from  Greenwood  Furnace,  Orange  Co ,  N  Y 

II  Meroxene  from  granite,  Butte,  Mont 

III  Lepidomelane  from  eleohte  syenite  Litchfield,  Maine 

IV  Brown  phlogopite  from  Burgess,  Can 

Before  the  blowpipe  the  dark,  ferruginous  varieties  fuse  easily  to  a 
black  glass,  the  lighter  colored  varieties  with  greater  difficulty  to  a 
yellow  glass  Their  powder  reactions  are  strongly  alkaline  The 
minerals  are  not  attacked  by  HC1  but  are  decomposed  by  strong 
EfeSO*  In  the  closed  tube  all  varieties  give  a  little  water 

The  biotitcs  are  distinguished  from  all  other  minerals  except  the  other 
micas  by  perfect  cleavage  and  from  other  micas  by  their  color,  solubility 
in  strong  sulphuric  acid  and  pleochroism 

The  commoner  alteration  products  of  biotite  are  a  hydrated  biotite, 
chlorite  (p  428),  epidote,  sillimamte  and  magnetite,  if  the  mica  is 
ferriferous  At  the  same  time  there  is  often  a  separation  of  quartz 
Phlogopite  alters  to  a  hydrophlogopite  and  to  penmnite  (p.  429),  and 
talc  (p  401) 

Syntheses  —The  biotites  are  common  products  of  smelting  operations. 
They  have  been  made  by  fusing  silicates  of  the  proper  composition  with 
sodium  and  magnesium  fluorides 

Occurrences  and  Origin  — The  biotites  are  common  constituents  of 
igneous  and  metamorphic  rocks  and  pegmatite  dikes  They  also  are 
common  alteration  products  of  certain  silicates,  such  as  hornblende 
and  augite  They  are  present  m  sedimentary  rocks  principally  as  the 
products  of  weathering 

Uses — Phlogopite  is  used  as  an  insulator  in  electrical  appliances 
and  to  a  less  extent  for  the  same  purposes  as  those  for  which  ground 
muscovite  is  employed  No  "amber  mica"  is  produced  in  the 
United  States  Most  of  that  used  in  this  country  is  imported  from 



Margante  (Ca(AlO)2(AlOH)2(SiO4)2) 

Margante,  the  calcium  mica,  is  like  biotite  in  the  habit  of  its  crys- 
tals, which,  however,  are  not  so  well  formed  as  these  Usually  the  min- 
eral occurs  in  tabular  plates  with  hexagonal  outlines  but  without  side 
planes  It  occurs  also  as  scaly  aggregates 

Analyses  of  specimens  from  Gamsville,  Ga  (I),  and  Peekslull,  N  Y 
(II),  gave 

Si02       A1203      FeO        MgO       CaO      Na20    H20         Total 

I  31  72      50  03  12      ii  57      2  26      4  88        100  58 

II  32  73      46  58      5  12        i  oo      ii  04  4  49        100  96 

The  mineral  has  a  pearly  luster  on  its  basal  planes,  and  a  glassy  luster 
on  other  planes  Its  color  is  while,  yellowish,  or  gray  and  its  streak 
white  It  is  transparent  or  translucent  Its  cleavage  is  not  as  perfect 
as  in  the  other  micas,  and  its  cleavage  plates  are  less  clastic  Its  hard- 
ness vanes  from  3  to  over  4  and  its  density  is  3  It  is  a  mica  of  the 
first  order 

Before  the  blowpipe  it  swells,  but  fuses  with  great  difficulty  It 
gives  water  m  the  closed  tube  and  is  attacked  by  acids 

Occurrence — Margante  is  associated  with  corundum  It  is  also 
present  in  some  chlorite  schists  In  all  cases  it  is  of  mctamorphic  origin 

Localities — It  occurs  in  the  Zillerthal,  Tyiol,  at  Campo  Longo,  m 
Switzerland,  at  the  emery  localities  m  the  Grecian  Archipelago,  at 
the  emery  mines  near  Chester,  Mass  ,  in  schist  inclusions  in  mica 
dionte  at  Peekskill,  N  Y  ,  with  corundum  at  Village  Green,  Penn , 
at  the  Cullakenee  Mine,  in  Clay  Co ,  N.  C,  and  at  corundum  local- 
ities in  Georgia,  Alabama  and  Virginia 


Zinnwaldite  ((Li-  K-  Na)3FeAl(Al(F-  OH))2Si5Oi0) 

The  pnncipal  hthmm-iron  mica,  zmnwaldite,  is  a  very  complex 
mixture  that  occurs  m  several  forms  so  well  characterized  that  they  have 
received  different  names  All  of  them  contain  lithium,  iron  and  fluorine, 
but  in  such  different  proportions  that  it  has  not  been  possible  to  ascribe 
to  them  any  one  generally  acceptable  formula  Some  of  the  most  im- 
portant of  these  varieties  have  compositions  corresponding  to  the  fol- 
lowing analyses 



Si02.      40  19  59  25  s1  46  45  87 

22    79  12    57  l6    22  22    $O 

19  78  2  21  66 

FeO  93  7  66  ii  6r 

MnO                  2  02  06  i  75 

NasO  7  63  95  42 

K20                  7  49  5  37  I0  65  10  46 

Li20                  3  06  g  04  4,83  3  28 

F                       3  99  7  3^  7  44  7  94 

Total        99  32  102  ii  102  71  105  48 

—  0=F=         97  64  99  05  99  60         102  15 

I  Rabenghmmer  from  Altenberg  Saxony     Greenish  black  with  greenish  gray 

streak     Sp  gr  =3  146-3  IQO 

II  Polyhlhiomlc  from  Kangerluarsuk,  Greenland     White  or  light  green  plates 
Sp  gr  =281 

III  Cryophyllitc  from  Rrxkporl,  Mass,    Strongly  plewhroic  green  and  brown- 

ish led  crystals     Sp  gr  «  2  QOQ     Contains  also  17  MgO  and  i  06  HgO 

IV  Zinnwaldile  from  Zmnwald,  Bohemia.    Plates,  white,  yellow  or  greenish 
gray     Sp.  gr  =2  956-2,087     Contains  also  r;i  IIjO  and  08 

Zinnwalchle  occuis  m  crystals  with  u,n  axial  ratio  very  near  that 
of  biotitc,  and  a  tabular  habit  Twins  arc  like  those  of  biotitc  with 
ooP(iio)  the  twinning  plane 

It  has  a  pearly  luster,  is  of  many  colors,  particularly  violet,  gray, 
yellow,  brown  and  dark  gieen  and  is  strongly  plcochroic.  Its  streak  is 
light,  Us  hardness  between  2  and  3  and  its  density  between  2.8  and  3  2. 
It  is  a  mica  of  the  second  01  der 

Before  the  blowpipe  it  fuses  to  a  dark,  weakly  magnetic  bead  It  is 
attacked  by  acids 

Qccumnte  and  Lotahtic\  —  Zmnwaldite  is  found  m  certain  ore  veins, 
m  granites  containing  cassiterite,  and  m  pegmatites  Its  origin  is  as- 
cribed to  pneumatolytic  processes  Us  principal  occuirences  are  those 
referred  to  m  connection  with  the  analyses 


The  alkali  micas  include  those  m  which  the  principal  metallic  con- 
stituents besides  aluminium  are  lithium,  potassium  and  sodium.  All 
these  metals  are  present  in  each  of  the  recognized  varieties  of  the 
alkali  micas,  but  in  each  variety  one  of  them  predominates  That  in 
which  lithium  is  prominent  is  known  as  lefodolite;  that  m  which  potas- 


sium  is  most  abundant  is  muscowte,  and  that  in  which  sodium  is 
most  prominent  is  paragomte  Muscovite  is  common  Lepidolite  is 
abundant  in  a  few  places  Paragomte  is  rare  The  first  two  are  im- 
portant economically  All  are  micas  of  the  first  order,  except  a  few 
iepidolites,  and  all  are  light  colored 

Another  mica,  which  is  usually  regarded  as  a  distinct  variety  of 
muscovite,  or,  at  any  rate,  as  being  very  closely  related  to  the  mineral 
is  roscoelite  In  this,  about  two-thirds  of  the  AlgOs  m  muscovite  is 
replaced  by  VgOj,  It  is  a  rare  green  mica  which  is  utilized  as  an  ore 
of  vanadium, 

Lepidolite  ((Li- K-Na)2((Al-Fe)OH)2(SiO,Oa) 

Lepidohte  occurs  almost  exclusively  as  aggregates  of  thin  plates 
with  hexagonal  outlines  Crystals  are  so  poorly  developed  that  a  satis- 
factory axial  ratio  has  not  been  determined  Its  variation  m  composi- 
tion is  indicated  by  the  analyses  of  white  and  purple  varieties  from 
American  localities 






51  52 

49  52 

5*  12 

51  25 

25  96 

28  So 

22  70 

25  62 






24  , 




I  34* 








4  9° 

3  87 

S  12 

4  3* 

i  06 


2  28 

T  94 

11  01 

8  82 

10  60 

10  65 


3  73 


.  »  * 

5  So 

S  18 


7  06 


i  72 

2  Og 

i  60 













(lessO=F)  99  45  100  53         99  74  99.63 

I.  Like-purple  granular  lepidohte  from  Rumford,  Maine 
II  White  variety  from  Norway,  Maine 
III  Red-purple  variety  from  Tourmaline  Queen  Mine,  Pala,  Cal.    Contains 

also  04  PjOj 
IV.  White  variety  from  Pala,  Cal 



The  mineral  is  while,  rose  or  light  purple,  gray  or  greenish     The 
rose  and  purple  varieties  contain  a  little  manganese     The  streak 
of  all   lepidolites  is  white,  their  luster  pearly,   their  hardness   2  5-4 
and  density  28-29     The  refractive  indices  of  a  typical  variety  are 
0=i  5975*  7  ==16047 

Lepidohte  fuses  easily  to  a  white  enamel  and  at  the  same  time  colors 
the  flame  red  It  is  difficultly  attacked  by  acids,  but  after  heating  is 
easily  decomposed 

Cookeitc  fiom  Maine  and  California  is  probably  a  weathered  lepido- 
hte  Its  analyses  concspond  to  the  foimula,  Li(Al(OH)2)3(SiOa)2 

Occutrencc  —  The  mincial  occuis  puncipally  in  pegmatites  in  which 
lubelhte  (p  435),  and  other  bi  ight-colored  tourmalines  exist  and  on 
the  borders  of  granite  masses  and  in  rocks  adjacent  to  them  It  is 
often  zonally  mtergrown  with  muscovitc  In  all  cases  it  is  probably  a 
pncunutolytic  pioduct,  or,  at  least,  is  produced  by  the  aid  of  magrnatic 

Localities  —  The  mineral  occurs  in  nearly  all  districts  producing  tin, 
and  also  in  those  producing  gem  tourmaline  Its  best  known  foreign 
localities  are  Jekatcrmbuig,  Russia,  Rozna,  Moravia,  Schmttenhofen, 
Bohemia,  and  Penig,  Sa\ron>  In  the  United  States  it  is  found  in  large 
quantities  at  Hebron,  Pans,  and  other  points  in  western  Maine,  m  the 
tin  mines  of  the  southern  Black  Hills,  South  Dakota,  and  in  the  tourma- 
line localities  m  the  neighborhood  of  Pala,  San  Diego  Co  ,  Cal 

Usei>  —  Lepidohte  is  utilized  to  a  slight  extent  m  the  manufacture  of 
lithium  compounds,  which  are  employed  m  the  preparation  of  lithia 
waters  medicinal  compounds,  salts,  used  in  photography  and  m  the 
manufacture  of  fireworks  and  stoiage  batteries 

Muscovite  (Ha(K  Na)Alj(SiOi)a) 

Muscovitc  is  one  of  the  most  common,  and  at  the  same  time  the 
most  important,  of  the  micas  Because  of  its  transparency  it  is  em- 
ployed for  many  purposes  for  which  the  darker  biotite  is  not  suitable 

While  predominantly  a  potash  mica,  nearly  all  muscovite  contains 
some  soda,  due  to  the  isomorphous  mixtuie  of  the  paragomte  molecule. 
Two  typical  analyses  are  quoted  below: 

Si02    AlsOs  FeaOs    FeO  MnO  MgO  CaO   NaaO    KS0     HaO      F    Total 

I     44  39    35  7°    *  09    i  07      tr  ro    2  41      9  77    5  88    .72  10113 

II.    46  54    34  96    i  59  .      32  4*     *o  38    5  43  99  63 

I.  Broad  plates  of  muscovite  bordered  by  lepidoiite,  Auburn,  Maine. 
II   Greenish  muscovite,  Auburn,  Maine     Total  less  Q«F  n  100.83 



The  crystals  are  usually  tabular  and  frequently  orthorhombic  or 
hexagonal  in  habit,  though  the  etch  figures  on  their  basal  pknes  reveal 
clearly  their  monoclimc  symmetry  (Fig  194)  If  onentated  to  corre- 
spond with  crystals  of  biotite  their  a\ial  constants  are  a  b  c==  5774 
i  .  3  3128,  0=89°  54',  and  their  principal  planes  oP(ooi),  oo  p  &  (Oio) 
|P  ob  (023),  4P(44i)  and  -2P(22i)  (Fig  IQS) 

Twins  like  those  of  biotite  are  not  uncommon  in  some  localities 
Muscovite  is  colorless  or  of  some  light  shade  of  green,  yellow  or  red 
It  has  a  glassy  luster,  a  perfect  cleavage  parallel  to  the  base,  a  haidness 
of  2  and  a  density  of  2  76-3  i  Pleochroism  is  marked  in  dncctions 
perpendicular  and  parallel  to  the  cleavage,  the  color  of  the  crystals, 
when  viewed  in  the  direction  perpendicular  to  the  cleavage  being  lighter 

FIG  194 

I'll,     1 1)5. 

FIG  194 — Etch  Figures  on  oP(ooi)  of  Muscovite,  Exhibiting  Monodmu,  Symmetry 
FIG   195 — Muscovite  Crystal  with  — 2P,  221  (Af)t  oP,  ooi  (<),    <wPw,  oio  (/;), 

and  3P«>,  023  (r) 

than  when  viewed  parallel  to  the  cleavage  The  optic  al  angle  is  com- 
paratively large  (56°-76°),  in  this  respect  being  vciy  different  from  that 
of  biotite  which  is  small  (2°-22°)  The  mineral  is  a  nonconductor 
of  electricity  at  ordinary  temperatures  and  a  poor  conductor  of  heat. 
Its  refractive  indices  vary  somewhat  with  composition  For  yellow  light 
intermediate  values  are  as  follows  a~  i  5619,  j8«- 1.5947,  7=  1,6027, 

Before  the  blowpipe  thin  flakes  of  muscovite  fuse  on  their  edges  to  a 
gray  mass  In  the  dosed  tube  the  mineral  yields  water  which,  in  some 
cases,  reacts  for  fluorine  It  is  insoluble  m  acids  under  ordinary  coi> 
ditions,  but  is  decomposed  on  fusion  with  alkaline  carbonates. 

Muscovite  is  very  stable  under  surface  conditions  Its  principal 
change  is  into  a  partially  hydrated  substance,  which  may  be  culled 
hydromuscovite.  It  alters  also  into  scaly  chlontic  products,  into 
steatite  (p  401),  and  serpentine  (p,  398). 


DomounU  is  a  dense  fine-grained  aggregate  of  muscovite,  often 
forming  pseudomorphs  after  other  minerals 

Senc^te  is  a  yellowish  or  greenish  muscovite  that  occurs  in  thin, 
curved  plates  m  some  schists 

Fwhsite  is  a  chromiferous  variety  of  an  emerald-green  color  from 
Schwarzenstem,  Tyiol 

Synthesis  — Crystals  of  muscovite  have  been  made  by  fusing  anda- 
lusite  with  potassium  fluo-sihcate  and  aluminium  fluoride 

Occurrence — Muscovite  occurs  in  large,  ill-defined  crystals  in  peg- 
matites, and  in  smaller  flakes  in  giamtes  and  othci  acid  igneous  rocks, 
in  some  sandstones  and  slates  and  m  various  schists  and  other  meta- 
morphic  rocks  It  is  found  also  in  veins  It  is  m  some  cases  an  orig- 
inal pyrogemc  mineral,  m  other  cases  a  mctamorphic  mineral  and  m 
still  other  cases  a  sccondaiy  mineral  resulting  from  the  alteration  of 
alkaline  aluminous  silicates 

Localities  — The  mineral  occurs  m  all  regions  where  pegmatites  and 
acid  igneous  rocks  c\ist  It  is  mined  m  North  Carolina,  South  Dakota, 
New  Hampshire,  Virginia  and  other  states  While  phlogopitc  (amber 
mica)  is  produced  in  some  countries  all  the  mica  produced  in  this  country 
is  of  the  muscovite  variety 

t/iw  —Muscovite  is  used  m  two  forms,  (i)  as  sheet  mica,  and  (2) 
as  ground  mica.  The  sheet  mica  comprises  thm  cleavage  plates  cut 
into  shapes  It  is  used  in  making  gas-lamp  chimneys,  lamp  shades,  and 
windows  in  stoves.  The  greater  portion  is  used  as  insulators  m 
electrical  appliances,  though  for  some  forms  of  electrical  apparatus  the 
amber  mica  js  better  Because  of  the  comparatively  high  cost  of  large 
mica  plates,  small  plates  are  sometimes  built  up  into  larger  ones  The 
ground  mica  consists  of  small  crystals  and  the  waste  from  the  manu- 
facture of  sheet  mica  giound  very  fine.  It  is  used  in  the  manufacture 
of  wall  paper,  heavy  lubucants  and  fancy  paints  It  is  also  mixed  with 
shellac  and  melted  into  desired  forms  for  electrical  insulators 

Production  — The  total  value  of  the  mica  produced  in  the  United 
Stales  during  1912  was  $355,804,  divided  as  follows.  1,887,201  Ib  sheet 
mica,  valued  at  $310,254  and  3,512  tons  ground  mica,  valued  at  $45,550 
Of  this  North  Carolina  produced  454,653  11),  of  sheet  mica,  valued  at 
$187,501  and  2,347  tons  of  scrap  mica,  valued  at  $29,798,  or  a  total 
value  for  both  kinds  of  mica  of  $217,299  The  imports  of  sheet  mica 
during  the  same  year  amounted  to  $502,163,  of  which  241,124  Ib , 
valued  at  $155,686  was  trimmed  and  the  balance  untnmmed  The 
imports  during  1912  were  valued  at  $748,973,  and  the  domestic  produc- 
tion at  $331,896- 


Roscoelite  may  be  regarded  as  a  muscovite  in  which  a  large  portion 
of  the  AkOs  has  been  replaced  by  V20s  A  specimen  from  Lotus,  Eldo- 
rado Co ,  Cal ,  gave 

Si02     Ti02    A1203     V203     FeO    MgO     K80     H,0-    H,0+     Total 
45  17      78     ii  54    24  01     i  60    i  64      10  37         40        4  29      99  80 

besides  traces  of  Li20  and  Na20 

The  mineral  occurs  as  clove-brown  or  green  scales  with  a  specific 
gravity  of  2  92-2  94  It  is  translucent  and  has  a  pearly  luster  and  a 
strong  pleochroism.  Its  refiactive  indices  for  sodium  light  are,  <x=  1,610, 

0=1685,7=1  704 

Before  the  blowpipe  it  fuses  to  a  black  glass.  It  gives  the  usual 
reactions  for  vanadium  m  the  beads  and  is  only  slightly  alTccted  by 
acids  It  has  been  found  associated  with  gold  m  small  veins  ncui  Lotus, 
Eldorado  Co.,  California,  in  seams  composed  of  roscochte  and  quartz 
between  the  beds  of  a  sandstone  in  the  high  plateau  region  of  south- 
western Colorado,  and  as  a  cement  of  minute  scales  between  the  grams 
of  the  sandstone  on  both  sides  of  the  seams.  In  all  cases  it  appears  to 
have  been  deposited  by  percolating  water,  possibly  of  magmatic  origin 

The  impregnated  sandstone  is  mined  as  a  source  of  vanadium  The 
material,  which  contains  an  average  of  about  3  per  cent  of  metallic 
vanadium  is  concentrated  by  chemical  processes,  and  the  concentrates 
are  manufactured  into  ferro-vanadium.  Most  of  the  vanadium  pro- 
duced in  the  United  States  is  made  from  this  ore, 

Paragonite  ^(Na-KJAlsCSiO-Oa) 

Paragonite,  the  sodium  mica,  differs  from  muscovite  mainly  in  com- 
position Both  contain  sodium  and  potassium  but  in  puragomte  the 
sodium  molecule  is  in  excess 

The  analysis  quoted  below  is  made  on  a  sample  from  Monte  Cam- 
pione,  in  Switzerland 

Si02       AI203          Fe203        Na20         K20         H20       Total 
47  75       40  10  tr.  6  04          i  12  4  58       99  59 

It  occurs  in  the  same  associations  as  some  forms  of  muscovite  but  it 
is  much  less  common.  It  apparently  occurs  most  abundantly  in  certain 
fine-grained  mica  schists  to  which  the  name  paragonite  schists  has  been 
given,  It  i§  m  ail  known  cases  a  product  of  dynamic  metamorphism* 




Beryl  (BeaAl2(Si03)o) 

BFRYL  is  a  frequent  constituent  of  coarse-grained  granites.  It  is 
important  as  a  gem  matciial,  and  is  particularly  interesting  because  of 
the  many  physical  investigations  that  have  been  made  with  the  aid  of  its 

Although  the  mineral  is  essentially  a  beryllium  alummo-rnetasilicate, 
it  usually  contains  also  a  little  FesOa  and  MgO,  in  many  cases  small 
quantities  of  the  alkalies,  and  in  some  cases  also  caesium.  Analyses  of 
a  green  beryl  from  North  Carolina,  an  aquamarine  from  Stoneham,  Me  , 
and  a  light-colored  crystal  from  Hebron  are  given  below 

Si02  AfcOi  Fe20;j  BeO    FeO  Na20  Li20  Cs20    H20  Total 

I.  66  84  19  05        .  14  n   .          .......  100  oo 

II.  66  28  18  60      .  13  61   ,22    ,,                ,.          .83  90  54 

III  65  54  17  75      21  13  73             71     ...        2  01  100  39 

IV,  62  44  17,74      40  ii  36   ,38   i  13    I  60  3.60    2.03  100  30 

I  Theoretical 
II,  Alexander  Co,,  N.  C, 
II  I  Stoneham*  Me.;  ako.o6%CaO. 
IV,  Hebron,  Me 

The  mineral  occurs  massive  without  distinct  crystal  form  and  also  in 
granular  and  columnar  aggregates,  but  its  usual  method  of  occurrence  is 
in  sharp  and,  in  some  cases,  very  large  columnar  crystals  with  a  distinct 
hexagonal  habit  (dihexagonal  bipyramidal  class),  and  an  axial  ratio 
i  :  4989.  The  forms  found  on  nearly  all  crystals  are  oo  P(tolo), 
ooP2(ii2o),  oP(oooi),  P(ion),  P2(ii22)  and  2P2(ii2i)  (Fig  196), 
In  addition,  there  are  present  on  many  crystals  other  prismatic  forms 
and  the  pyramids  3?f  (2131)  and  aP(ao3i).  Other  crystals  are  highly 




modified  (Fig  197),  the  total  number  of  forms  that  have  been  identified 
approximating  50  The  angle  icli  Aoi7i  =  28°  55'  Some  crystals 
are  very  large,  measuring  2  to  4  feet  in  length  and  i  ft  in  diameter 

Beryl  has  a  glassy  luster  It  is  transparent  or  translucent  It  is 
colorless  or  of  some  light  shade  of  green,  red,  or  blue  Its  streak  is 
white,  hardness  7-8  and  density  2  6-2  8  Its  cleavage  is  very  imperfect 
but  there  is  frequently  a  parting  parallel  to  the  base  Pleochroism  is 
noticeable  in  green  and  blue  crystals  Its  refractive  indices  for  yellow 
light  at  20°  are  co=  i  5740,  e=  i  5690  They  become  greater  with  increas- 
ing temperature 

Before  the  blowpipe  colorless  varieties  become  milky,  but  others  are 

FIG  tg6  1'ic,  197 

FIG  196— Beryl  Crystals  with  °op,  ioTo  (w),  oP  oooi  (c),    <»  P2,  1120  (a),   P, 
loii  (p)  and  2?2,  1 121  00 

FIG  197  — Beryl  Crystal  with  m,  c,  p  and  A  as  m  Fig  196      Also  2p,  202 1  (M)  and 

3Pg,  2131  M 

unchanged  except  at  very  high  temperatures  when  sharp  edges  arc  fused 
to  a  porous  glass  The  mineral  is  not  attacked  by  acids. 

Beryl  is  distinguished  from  apatite,  which  it  much  resembles,  by  its 
greater  hardness 

It  alters  to  mica  and  kaolin  (p  404) 

Syntheses — Beryl  crystals  have  been  formed  by  long  heating  of 
8162,  AkOs  and  BeO  m  a  melt  of  the  molybdate  or  vanadate  of  lithium, 
and  by  precipitating  a  solution  of  beryllium  and  aluminium  sulphates 
with  sodium  silicate  and  heating  the  dried  precipitate  with  boric  acid 
in  a  porcelain  oven 

Occurrence  —The  mineral  occurs  as  an  accessory  constituent  m  peg- 
matites and  granites,  in  crystalline  schists,  especially  mica  schists  and 


gneisses,  m  ore  veins  and  sometimes  in  clay  slates  and  bituminous  lime- 

Uses — The  transparent  varieties  are  utilized  as  gems,  under  t